U.S. patent number 10,756,946 [Application Number 16/300,604] was granted by the patent office on 2020-08-25 for dormant mode measurement optimization.
This patent grant is currently assigned to Telefonaktiebolaget LM Ericsson (publ). The grantee listed for this patent is Telefonaktiebolaget LM Ericsson (publ). Invention is credited to Robert Baldemair, Martin Hessler, Eleftherios Karipidis, Bo Lincoln, Torgny Palenius, Eliane Semaan.
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United States Patent |
10,756,946 |
Lincoln , et al. |
August 25, 2020 |
Dormant mode measurement optimization
Abstract
Methods performed by a wireless device operating in a dormant
mode comprise performing a measurement on each of a plurality of
resources from a predetermined set of resources or demodulating and
decoding information from each of a plurality of resources from a
predetermined set of resources, such as a set of beams. The methods
further include evaluating the measurement or the demodulated and
decoded information for each of the plurality of resources against
a predetermined criterion, and then discontinuing the performing
and evaluating of measurements, or discontinuing the demodulating
and decoding and evaluation of information, in response to
determining that the predetermined criterion is met, such that one
or more resources in the predetermined set of resources are neither
measured nor demodulated and decoded. The methods further comprise
deactivating receiver circuitry, further in response to determining
that the predetermined criterion is met.
Inventors: |
Lincoln; Bo (Lund,
SE), Baldemair; Robert (Solna, SE),
Hessler; Martin (Linkoping, SE), Karipidis;
Eleftherios (Stockholm, SE), Palenius; Torgny
(Barseback, SE), Semaan; Eliane (Sundbyberg,
SE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Telefonaktiebolaget LM Ericsson (publ) |
Stockholm |
N/A |
SE |
|
|
Assignee: |
Telefonaktiebolaget LM Ericsson
(publ) (Stockholm, SE)
|
Family
ID: |
58745329 |
Appl.
No.: |
16/300,604 |
Filed: |
May 12, 2017 |
PCT
Filed: |
May 12, 2017 |
PCT No.: |
PCT/SE2017/050489 |
371(c)(1),(2),(4) Date: |
November 12, 2018 |
PCT
Pub. No.: |
WO2017/196247 |
PCT
Pub. Date: |
November 16, 2017 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20190158345 A1 |
May 23, 2019 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
15154403 |
May 13, 2016 |
10367677 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W
24/10 (20130101); H04B 7/0617 (20130101); H04W
52/028 (20130101); H04W 52/0245 (20130101); H04L
41/0233 (20130101); H04B 7/0695 (20130101); H04L
41/0816 (20130101); H04W 52/0251 (20130101); H04W
52/0274 (20130101); H04J 11/0059 (20130101); H04J
11/0056 (20130101); H04J 11/0079 (20130101); H04W
52/0229 (20130101); H04B 7/0626 (20130101); H04W
28/0221 (20130101); Y02D 30/00 (20180101); H04W
16/28 (20130101); Y02D 30/70 (20200801) |
Current International
Class: |
H04W
52/02 (20090101); H04W 24/10 (20090101); H04B
7/06 (20060101); H04L 12/24 (20060101); H04J
11/00 (20060101); H04W 28/02 (20090101); H04W
16/28 (20090101) |
References Cited
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|
Primary Examiner: Hamza; Faruk
Assistant Examiner: Guadalupe Cruz; Aixa A
Attorney, Agent or Firm: Murphy, Bilak & Homiller,
PLLC
Claims
What is claimed is:
1. A method, in a wireless device, for operating in a wireless
communications network, the method comprising: operating in a
dormant mode, wherein operating in the dormant mode comprises
intermittently activating receiver circuitry to monitor and/or
measure signals; and, while in dormant mode and while the receiver
circuitry is activated: performing a measurement on each of a
plurality of resources from a predetermined set of resources or
demodulating and decoding information from each of a plurality of
resources from a predetermined set of resources, where the
resources in the predetermined set of resources are each defined by
one or more of a beam, a timing, and a frequency; evaluating the
measurement or the demodulated and decoded information for each of
the plurality of resources against a predetermined criterion;
discontinuing the performing and evaluating of measurements or
discontinuing the demodulating and decoding and evaluation of
information, in response to determining that the predetermined
criterion is met, such that one or more resources in the
predetermined set of resources are neither measured nor demodulated
and decoded; and deactivating the activated receiver circuitry,
further in response to determining that the predetermined criterion
is met.
2. The method of claim 1, wherein the resources in the
predetermined set of resources are each defined as a beam.
3. The method of claim 1, wherein the predetermined criterion
comprises one or more of the following: that a received power level
or a measured signal-to-interference-plus-noise ratio (SINR) or a
signal-to-noise ratio (SNR) is above a predetermined threshold, for
one or for a predetermined number of resources; that cell
information can be correctly decoded from one or for a
predetermined number of resources; and that decoded information
from one or for a predetermined number of resources instructs a
change in operation for the wireless device.
4. The method of claim 1, wherein said discontinuing is performed
in response to determining that the predetermined criterion is met
for one of the resources.
5. The method of claim 1, further comprising, prior to said
performing or demodulating and decoding, and prior to said
evaluating, discontinuing, and deactivating, determining a priority
order for the predetermined set of resources, from highest to
lowest, wherein said performing or demodulating and decoding is
according to the priority order, from highest to lowest.
6. The method of claim 5, wherein determining the priority order
for the predetermined set of resources is based on one or more of:
radio resource timing for one or more of the resources; and
measured signal qualities or measurement properties from previous
measurements of one or more of the resources.
7. The method of claim 5, wherein determining the priority order
for the predetermined set of resources is based on information
regarding likelihood of usefulness for one or more of the
resources, said information being received from other sources or
cell neighbor lists.
8. A wireless device for operation in a wireless communications
network, the wireless device comprising receiver circuitry and
processing circuitry operatively coupled to the receiver circuitry
and configured to: operate in a dormant mode, wherein operating in
the dormant mode comprises intermittently activating the receiver
circuitry to monitor and/or measure signals; and, while in dormant
mode and while the receiver circuitry is activated: perform a
measurement on each of a plurality of resources from a
predetermined set of resources or demodulate and decode information
from each of a plurality of resources from a predetermined set of
resources, where the resources in the predetermined set of
resources are each defined by one or more of a beam, a timing, and
a frequency; evaluate the measurement or the demodulated and
decoded information for each of the plurality of resources against
a predetermined criterion; discontinue the performing and
evaluating of measurements or discontinue the demodulating and
decoding and evaluation of information, in response to determining
that the predetermined criterion is met, such that one or more
resources in the predetermined set of resources are neither
measured nor demodulated and decoded; and deactivate the activated
receiver circuitry, further in response to determining that the
predetermined criterion is met.
9. The wireless device of claim 8, wherein the resources in the
predetermined set of resources are each defined as a beam.
10. The wireless device of claim 9, wherein the predetermined
criterion comprises one or more of the following: that a received
power level or a measured signal-to-interference-plus-noise ratio
(SINR) or a signal-to-noise ratio (SNR) is above a predetermined
threshold, for one or for a predetermined number of resources; that
cell information can be correctly decoded from one or for a
predetermined number of resources; that decoded information from
one or for a predetermined number of resources instructs a change
in operation for the wireless device.
11. The wireless device of claim 8, wherein the processing
circuitry is configured to carry out said discontinuing in response
to determining that the predetermined criterion is met for one of
the resources.
12. The wireless device of claim 8, wherein the processing
circuitry is further configured to, prior to said performing or
demodulating and decoding, and prior to said evaluating,
discontinuing, and deactivating, determine a priority order for the
predetermined set of resources, from highest to lowest, wherein the
processing circuitry is configured to carry out said performing or
demodulating and decoding is according to the priority order, from
highest to lowest.
13. The wireless device of claim 12, wherein the processing
circuitry is configured to determine the priority order for the
predetermined set of resources based on one or more of: radio
resource timing for one or more of the resources; and measured
signal qualities or measurement properties from previous
measurements of one or more of the resources.
14. The wireless device of claim 12, wherein the processing
circuitry is configured to determine the priority order for the
predetermined set of resources based on information regarding
likelihood of usefulness for one or more of the resources, said
information being received from other sources or cell neighbor
lists.
Description
TECHNICAL FIELD
The present disclosure is generally related to the performing of
measurements for radio resource management, and is more
particularly related to methods and apparatus for performing
measurements in dormant mode.
BACKGROUND
In any cellular system, it is of very high importance that battery
powered, mobile nodes (hereafter referred to as "user equipments,"
or "UEs") can spend most of their time in a low activity state to
preserve energy. Typically, a cellular system will have one or more
defined "active" modes, where the UE is controlled by the network
and is instructed to attach to a certain cell, do certain
measurements etc. The system will generally also have one or more
"idle" or "dormant" modes, where the UE typically listens only to
certain signals from the network and makes its own decisions
regarding which cell or cells to listen to, and when to report back
status updates.
Most UEs in most cellular systems today spend a majority of their
time in dormant mode, and therefore it is of utmost importance that
the UEs can consume as little power as possible in dormant
mode.
In a cellular system like as the 5.sup.th-generation radio access
network (RAN) currently being defined by the 3.sup.rd-Generation
Partnership (3GPP) and often referred to as "New Radio" or "NR,"
beamforming can be used for the transmission of cell information
signals. "Beamforming" here refers to a (usually) highly
directional transmission of the signal energy for a given signal or
set of signals, e.g., with 3-dB beam-widths of less, often
substantially less, than 90 degrees in the horizontal plane, for
downlink transmissions. While conventional transmissions are shaped
to some degree, e.g., to avoid transmitting excessive energy in a
vertical direction and/or to direct the majority of the signal
energy to a particular cell sector, the beamformed transmissions
discussed herein are intentionally shaped to a greater extent, so
that, for example, any given downlink beam provides useful signal
strengths only within a small fraction of the area that is
generally served by the transmitting node. Accordingly, to serve
the entire area, the transmitting node may make use of multiple,
and perhaps very many, beams, which may be time-multiplexed,
frequency-multiplexed, or both.
Beamforming cell information signals or broadcast signals, such as
so-called mobility reference symbols, rather than transmitting them
over an entire cell, may be done for several reasons. One reason is
to increase the effective antenna gain of the transmitter, e.g., to
compensate for higher path loss in high frequency bands or to
enable extended coverage at traditional frequencies. Another reason
is to obtain a rough spatial positioning of a UE, based on the
directionality of the beam.
Typically, the beamformed cell information signals will be time
multiplexed between beams so that high output power can be used for
each beam.
SUMMARY
With beamformed cell information signals, there is a multiplication
factor introduced with respect to the number of signals that a UE
in dormant mode must search for and measure. In a conventional
system where cell information is not beam-formed, there is
typically one signal to measure for each "cell"--for the same kind
of "cell" where cell information is beamformed, there can be
several tens of signals or beams, such as beams carrying mobility
reference signals, to search for. This can increase the power
consumption for a UE in dormant mode, especially if the signals are
time multiplexed, as search for such beams requires the UE receiver
to be on over long durations of time.
Embodiments disclosed herein to address these problems include
methods performed by a UE or other wireless device that is
operating in a dormant mode, where operating in the dormant mode
comprises intermittently activating receiver circuitry to monitor
and/or measure signals. These methods comprise, while the wireless
device is in this dormant mode, and while the receiver circuitry is
activated, performing a measurement on each of a plurality of
resources from a predetermined set of resources or demodulating and
decoding information from each of a plurality of resources from a
predetermined set of resources, where the resources in the
predetermined set of resources are each defined by one or more of a
beam, a timing, and a frequency. In some embodiments, the resources
in this predetermined set of resources are each defined as a beam.
The methods further include evaluating the measurement or the
demodulated and decoded information for each of the plurality of
resources against a predetermined criterion, and then discontinuing
the performing and evaluating of measurements, or discontinuing the
demodulating and decoding and evaluation of information, in
response to determining that the predetermined criterion is met,
such that one or more resources in the predetermined set of
resources are neither measured nor demodulated and decoded. The
methods further comprise deactivating the activated receiver
circuitry, further in response to determining that the
predetermined criterion is met.
In some embodiments, the predetermined criterion comprises one or
more of the following: that a received power level, or a measured
signal-to-interference-plus-noise ratio (SINR), or a
signal-to-noise ratio (SNR) is above a predetermined threshold, for
one or for a predetermined number of resources; that cell
information can be correctly decoded from one or for a
predetermined number of resources; and that decoded information
from one or for a predetermined number of resources instructs a
change in operation for the wireless device.
In some embodiments, the discontinuing is performed in response to
determining that the predetermined criterion is met for one of the
resources. In some embodiments, the method further comprises, prior
to said performing or demodulating and decoding, and prior to said
evaluating, discontinuing, and deactivating, determining a priority
order for the predetermined set of resources, from highest to
lowest, wherein said performing or demodulating and decoding is
according to the priority order, from highest to lowest. This
determining the priority order for the predetermined set of
resources may be based on one or more of any of the following, for
example: radio resource timing for one or more of the resources;
and measured signal qualities or measurement properties from
previous measurements of one or more of the resources. In some
embodiments, determining the priority order for the predetermined
set of resources is based on information regarding likelihood of
usefulness for one or more of the resources, the information being
received from other sources or cell neighbour lists.
Other embodiments disclosed herein include wireless devices adapted
to carry out a method according to any of those summarized above,
as well as corresponding computer program products and
computer-readable media.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 illustrates a high-level logical architecture for NR and
LTE.
FIG. 2 shows an NR and LTE logical architecture.
FIG. 3 illustrates LTE/NR UE states.
FIG. 4 includes a block diagram of filtered/windowed Orthogonal
Frequency-Division Multiplexing (OFDM) processing and shows mapping
of subcarriers to time-frequency plane.
FIG. 5 shows windowing of an OFDM symbol.
FIG. 6 illustrates basic subframe types.
FIG. 7 illustrates an example construction of a mobility and access
reference signal (MRS).
FIG. 8 shows tracking area configuration.
FIG. 9 is a signal flow diagram illustrating a Tracking RAN Area
(TRA) update procedure.
FIG. 10 shows options for beam shapes.
FIG. 11 is a signaling flow diagram illustrating an active-mode
mobility procedure.
FIG. 12 is a signaling flow diagram illustrating beam selection
based on uplink measurement.
FIG. 13 is a signaling flow diagram illustrating intra-node beam
selection based on uplink measurement.
FIG. 14 is a process flow diagram illustrating an example method in
a wireless device.
FIG. 15 is a process flow diagram illustrating another example
method in a wireless device.
FIG. 16 is a process flow diagram illustrating still another
example method in a wireless device.
FIG. 17 is a block diagram illustrating an example wireless
device.
FIG. 18 is a block diagram illustrating example radio network
equipment.
FIG. 19 is another block diagram illustrating an example wireless
device.
DETAILED DESCRIPTION
As discussed above, beamforming of cell information signals creates
potential problems with respect to power consumption for wireless
devices, or UEs, operating in dormant mode. In a conventional
system where cell information is not beam-formed, there is
typically one signal to measure for each cell, where "cell" refers
to the geographical area covered by the signals transmitted by a
cellular network access point--for the same kind of cell where cell
information is beamformed, there can be several tens of signals or
beams, such as beams carrying mobility reference signals, to search
for. This can increase the power consumption for a UE in dormant
mode, especially if the signals are time multiplexed, as search for
such beams requires the UE receiver to be on over long durations of
time.
The techniques and apparatus described herein address these
problems by reducing or limiting the power consumption in dormant
mode in a cellular system using beamformed cell information
signals, e.g., in a system like 3GPP's NR system. The techniques
and apparatus described herein do this by restricting the
measurement and cell search sequence in the UE, based on the signal
quality of the beamformed cell information signals that have
already been measured. For each measurement instance, the UE can
focus its search on previously known strong signals and
simultaneously search for new cells on that carrier. If the
previously known strong signals are verified to be strong enough,
the measurement sequence can be stopped, so that the UE need not
search for every possible cell information signal. Likewise, if one
or a predetermined number of cell information signals are received
and determined to be strong enough, the measurement sequence can be
stopped, again so that the UE does not search for every cell
information signal in a predetermined set of signals among which
the search is performed.
An advantage of several of the embodiments described herein is that
the measurement durations for a UE in dormant mode can be
drastically reduced in those circumstances where the UE can quickly
determine that it has "good enough" signal quality for one or more
cell information signals, where "good enough" means that the signal
quality meets one or more predetermined criteria.
Details of these techniques and apparatus, including a detailed
description of several specific embodiments, are provided below.
First, however, descriptions of several concepts, system/network
architectures, and detailed designs for several aspects of a
wireless communications network targeted to address the
requirements and use cases for fifth-generation networks (referred
to as "5G") are presented, to provide context for the disclosure of
the dormant mode operations that follow. It should be appreciated,
however, that an actual 5G network may include none, some, or all
of the detailed features described below. It will further be
appreciated that the techniques and apparatus described herein for
performing measurements in dormant mode are not limited to
so-called 5G networks, but may be used in and/or adapted for other
wireless networks.
In the discussion that follows, the wireless communications
network, which includes wireless devices, radio access networks,
and core networks, is referred to as "NR." It should be understood
that the term "NR" is used herein as simply a label, for
convenience. Implementations of wireless devices, radio network
equipment, network nodes, and networks that include some or all of
the features detailed herein may, of course, be referred to by any
of various names. In future development of specifications for 5G,
for example, other terms may be used--it will be understood that
some or all of the features described here may be directly
applicable to these specifications. Likewise, while the various
technologies and features described herein are targeted to a "5G"
wireless communications network, specific implementations of
wireless devices, radio network equipment, network nodes, and
networks that include some or all of the features detailed herein
may or may not be referred to by the term "5G."
NR targets new use cases, e.g. for factory automation, as well as
Extreme Mobile Broadband (MBB), and may be deployed in a wide range
of spectrum bands, calling for high degree of flexibility. Licensed
spectrum remains a cornerstone for NR wireless access but
unlicensed spectrum (stand-alone as well as license-assisted) and
various forms of shared spectrum (e.g. the 3.5 GHz band in the US)
are natively supported. A wide range of frequency bands are
supported, from below 1 GHz to almost 100 GHz. It is of principal
interest to ensure that NR can be deployed in a variety of
frequency bands, some targeting coverage at lower frequency regions
below 6 GHz, some providing a balance of coverage,
outdoor-to-indoor penetration and wide bandwidth up to 30 GHz, and
finally some bands above 30 GHz that will handle wide bandwidth use
cases, but possibly at a disadvantage to coverage and deployment
complexity. Both FDD and dynamic TDD, where the scheduler assigns
the transmission direction dynamically, are part of NR. However, it
is understood that most practical deployments of NR will likely be
in unpaired spectrum, which calls for the importance of TDD.
Ultra-lean design, where transmissions are self-contained with
reference signals transmitted along with the data, minimizes
broadcasting of signals. Terminals make no assumptions on the
content of a subframe unless they are scheduled to do so. The
consequence is significantly improved energy efficiency as
signaling not directly related to user data is minimized
Stand-alone deployments as well as tight interworking with LTE are
supported. Such interworking is desirable for consistent user
experience with NR when used at higher frequency ranges or at
initial NR rollout with limited coverage. The radio-access network
(RAN) architecture can handle a mix of NR-only, LTE-only, or
dual-standard base stations. The eNBs ("evolved Node Bs," 3GPP
terminology for a base station) are connected to each other via new
interfaces that are expected to be standardized. It is envisioned
that these new interfaces will be an evolution of the existing S1
and X2 interfaces to support features such as network slicing, on
demand activation of signals, user plane/control plane splits in
the core network (CN), and support for a new connected dormant
state, as described herein. As described below, LTE-NR base
stations may share at least integrated higher radio interface
protocol layers, such as the Packet Data Convergence Protocol
(PDCP) and Radio Resource Control (RRC) layers, as well as a common
connection to the evolved packet core (EPC).
NR separates dedicated data transmissions from system access
functions. The latter include system information distribution,
connection establishment functionality, and paging. Broadcast of
system information is minimized and not necessarily transmitted
from all nodes handling user-plane data. This separation benefits
beamforming, energy efficiency, and support of new deployment
solutions. In particular, this design principle allows
densification to increase the user-plane capacity without
increasing the signaling load.
A symmetric design with OFDM in both the downlink and the uplink
directions is detailed below. To handle the wide range of carrier
frequencies and deployments, a scalable numerology may be used. For
example, a local-area, high-frequency node uses a larger subcarrier
spacing and a shorter cyclic prefix than a wide-area, low-frequency
node. To support very low latency, a short subframe with fast
ACK/NACK (acknowledgement/negative acknowledgement) is proposed,
with the possibility for subframe aggregation for less
latency-critical services. Also, contention-based access is part of
NR, to facilitate fast UE initiated access. New coding schemes such
as polar codes or various forms of Low-Density Parity Check (LDPC)
codes may be used, instead of turbo codes, to facilitate rapid
decoding of high data rates with a reasonable chip area. Long
discontinuous-receive (DRX) cycles and a new UE state, RRC dormant,
where the UE RAN context is maintained, allow fast transition to
active mode with reduced control signaling.
Enabling full potential of multi-antenna technology is a
cornerstone of the NR design. Hybrid beamforming is supported and
advantages with digital beam forming are exploited. User-specific
beamforming through self-contained transmission is advantageous for
coverage, especially at high frequencies. For the same reason, UE
transmit (TX) beamforming is proposed as an advantageous component,
at least for high frequency bands. The number of antenna elements
may vary, from a relatively small number of antenna elements (e.g.,
2 to 8) in LTE-like deployments to many hundreds, where a large
number of active or individually steerable antenna elements are
used for beamforming, single-user MIMO and/or multi-user MIMO to
unleash the full potential of massive MIMO. Reference signals and
Medium Access Control (MAC) features are designed to allow
exploiting reciprocity-based schemes. Multi-point connectivity,
where a terminal is simultaneously connected to two or more
transmission points, can be used to provide diversity/robustness,
by transmitting the same data from multiple points.
NR includes a beam-based mobility concept to efficiently support
high-gain beam forming. This concept is transparent to both inter-
and intra-eNB beam handover. When the link beams are relatively
narrow, the mobility beams should be tracking UEs with high
accuracy to maintain good user experience and avoid link failure.
The mobility concept follows the ultra-lean design principle by
defining a set of network-configurable downlink mobility reference
signals that are transmitted on demand, when mobility measurements
from the UE are needed. Uplink measurement based mobility may also
be used, with suitable base stations supporting reciprocity.
5G Mobile Broadband (MBB) services will require a range of
different bandwidths. At the low end of the scale, support for
massive machine connectivity with relatively low bandwidths will be
driven by total energy consumption at the user equipment. In
contrast, very wide bandwidths may be needed for high capacity
scenarios, e.g., 4K video and future media. The NR air interface
focuses on high bandwidth services, and is designed around
availability of large and preferably contiguous spectrum
allocations.
High-level requirements addressed by the NR system described herein
include one or more of: 1) Support for higher frequency bands with
wider carrier bandwidth and higher peak rates. Note that this
requirement motivates a new numerology, as detailed below. 2)
Support for lower latency, which requires shorter and more flexible
Transmission Time Intervals (TTIs), new channel structures, etc. 3)
Support for very dense deployments, energy efficient deployments
and heavy use of beam forming, enabled by, for example removing
legacy limitations in relation to Cell-specific Reference Signal
(CRS), Physical Downlink Control Channel (PDCCH), etc. 4) Support
of new use cases, services and customers such as Machine-Type
Communication (MTC) scenarios including so-called
vehicle-to-anything (V2X) scenarios, etc. This can include more
flexible spectrum usage, support for very low latency, higher peak
rates etc.
Following is a description of the NR architecture, followed by a
description of the radio interface for NR. Following that is a
description of a variety of technologies and features that are
supported by the NR architecture and radio interface. It should be
understood that while the following detailed description provides a
comprehensive discussion of many aspects of a wireless
communications system, where numerous advantages are obtained by
combinations of many of the described features and technologies, it
is not necessary for all the technologies and features described
herein to be included in a system for the system to benefit from
the disclosed technologies and features. For example, while details
of how NR may be tightly integrated with LTE are provided, a
standalone version of NR is also practical. More generally, except
where a given feature is specifically described herein as depending
on another feature, any combination of the many technologies and
features described herein may be beneficial.
The NR architecture supports both stand-alone deployments and
deployments that may be integrated with LTE or, potentially, any
other communication technology. In the following discussion, there
is a lot of focus on the LTE integrated case. However, it should be
noted that similar architecture assumptions also apply to the NR
stand-alone case or to integration with other technologies.
FIG. 1 shows the high level logical architecture for an example
system supporting both NR and LTE. The logical architecture
includes both NR-only and LTE-only eNBs, as well as eNBs supporting
both NR and LTE. In the illustrated system, the eNBs are connected
to each other with a dedicated eNB-to-eNB interface referred to
here as the X2* interface, and to the core network with a dedicated
eNB-to-CN interface referred to here as the S1* interface. Of
course, the names of these interfaces may vary. As seen in the
figure, a core network/radio access network (CN/RAN) split is
evident, as was the case with the Evolved Packet Subsystem
(EPS).
The S1* and X2* interfaces may be an evolution of the existing S1
and X2 interfaces, to facilitate the integration of NR with LTE.
These interfaces may be enhanced to support multi-radio access
technology (RAT) features for NR and LTE Dual Connectivity (DC),
potentially new services (IoT or other 5G services), and features
such as network slicing (where, for example, different slices and
CN functions may require a different CN design), on demand
activation of mobility reference signals, new multi-connectivity
solutions, potentially new user plane/control plane splits in the
CN, support for a new connected dormant state, etc.
FIG. 2 shows the same logical architecture as FIG. 1, but now also
includes an example of an internal eNB architecture, including
possible protocols splits and mapping to different sites.
Following are features of the architecture discussed herein: LTE
and NR may share at least integrated higher radio interface
protocol layers (PDCP and RRC) as well as a common S1* connection
to packet core (EPC) The usage of LTE or NR for 5G capable UEs can
be transparent to the EPC (if desired). The RAN/CN functional split
over S1* is based on the current split used over S1.
Note, however that this does not exclude enhancements to the S1*
compared to S1, e.g., to support new features such as network
slicing. The 5G network architecture supports flexible placement
(deployment) of CN (EPC) functionality per user/flow/network slice
Centralization of PDCP/RRC is supported. The interface between
PDCP/RRC and lower layer entities need not be standardized
(although it can be), but can be proprietary (vendor-specific). The
radio interface is designed to support architecture flexibility
(allowing for multiple possible functional deployments, e.g.,
centralized/distributed). The architecture also supports fully
distributed PDCP/RRC (as is the case with LTE, today). To support
NR/LTE dual connectivity with centralized PDCP and RRC, NR supports
a split somewhere between the RRC/PDCP layers and the Physical
layer, e.g., at the PDCP layer. Flow control may be implemented on
X2*, supporting the split of PDCP and Radio Link Control (RLC) in
different nodes. PDCP is split into a PDCP-C part, used for
Signaling Radio Bearers (SRBs), and PDCP-U part, used for User
Radio Bearers (URBs), which can be implemented and deployed in
different places. The architecture supports Common Public Radio
Interface (CPRI)-based splits between a Radio Unit (RU) and a
Baseband Unit (BBU), but also other splits where some processing is
moved to the RU/Antenna in order to lower the required front-haul
bandwidth towards the BBU (e.g., when supporting very large
bandwidth, many antennas).
Note that despite the above discussion, alternative RAN/CN splits
are possible, while still maintaining many of the features and
advantages described herein.
This section discusses the different UE states in NR and LTE, with
focus on the UE sleep states, or "dormant" states. In LTE, two
different sleep states are supported: ECM_IDLE/RRC_IDLE, where only
the Core Network (CN) context is stored in the UE. In this state,
the UE has no context in the RAN and is known on Tracking Area (or
Tracking Area List) level. (The RAN context is created again during
transition to RRC_CONNECTED.) Mobility is controlled by the UE,
based on cell reselection parameters provided by the network.
ECM_CONNECTED/RRC_CONNECTED with UE configured DRX. In this state,
the UE is known on the cell level and the network controls the
mobility (handovers).
Out of these two states, ECM_IDLE/RRC_IDLE is the primary UE sleep
state in LTE for inactive terminals. RRC_CONNECTED with DRX is also
used, however the UE is typically released to RRC_IDLE after X
seconds of inactivity (where X is configured by the operator and
typically ranges from 10 to 61 seconds). Reasons why it may be
undesirable to keep the UE longer in RRC_CONNECTED with DRX include
limitations in eNB hardware capacity or software licenses, or other
aspects such as slightly higher UE battery consumption or a desire
to keep down the number of Handover Failures.
Given that initiating data transmission from ECM_IDLE in LTE
involves significantly more signaling compared to data transmission
from "RRC_CONNECTED with DRX", the "RRC_CONNECTED with DRX" state
is enhanced in NR to become the primary sleep state. The
enhancement includes adding support for UE-controlled mobility
within a local area, thus avoiding the need for the network to
actively monitor the UE mobility. Note that this approach allows
for the possibility that the LTE solution can be further evolved to
create a common RRC Connected sleep state for NR and LTE.
The following are features of this NR UE sleep state, which is
referred to herein as RRC_CONNECTED DORMANT (or RRC DORMANT for
short): It supports DRX (from milliseconds to hours). It supports
UE-controlled mobility, e.g., the UE may move around in a Tracking
RAN Area (TRA) or TRA list without notifying the network (TRA
(lists) span across LTE and NR). Transition to and from this state
is fast and lightweight (depending on the scenario, whether
optimized for energy saving or fast access performance), e.g., as
enabled by storing and resuming the RAN context (RRC) in the UE and
in the network.
When it comes to detailed solutions how this RRC DORMANT state is
supported, there are different options based on different level of
CN involvement. One option is as follows: The CN is unaware of
whether the UE is in RRC_CONNECTED DORMANT or RRC_CONNECTED ACTIVE
(described later), meaning the S1* connection is always active when
UE is in RRC_CONNECTED, regardless of sub state. A UE in RRC
DORMANT is allowed to move around within a TRA or TRA list without
notifying the network. Paging is triggered by the eNB when a packet
arrives over S1*. The MME may assist the eNB by forwarding page
messages when there is no X2* connectivity to all the eNBs of the
paging area. When the UE contacts the network from RRC DORMANT in a
RAN node that does not have the UE context, the RAN node tries to
fetch the UE context from the RAN node storing the context. If this
is successful, the procedure looks like an LTE X2 handover in the
CN. If the fetch fails, the UE context is re-built from the CN. The
area that the UE is allowed to move around without notifying the
network may comprise a set of Tracking RAN Areas, and covers both
LTE and NR RAT, thus avoiding the need to signal when switching RAT
in RRC DORMANT.
In addition to the RRC DORMANT state (optimized for power saving),
there is an RRC_CONNECTED ACTIVE (RRC ACTIVE) state used for actual
data transmission. This state is optimized for data transmissions,
but allows the UE to micro-sleep, thanks to DRX configuration, for
scenarios when no data is transmitted but a very quick access is
desired. This may be referred to as monitoring configuration within
the RRC ACTIVE state. In this state, the UE cell or beam level
mobility is controlled and known by the network.
Given a tight integration between NR and LTE, the desire to have a
RAN controlled sleep state in NR drives requirements to also
support a RAN-controlled sleep state in LTE for NR/LTE capable UEs.
The reason for this is that to support tight NR and LTE
integration, a common S1* connection is desirable for LTE and NR.
If a RAN-controlled sleep state is introduced on the NR side, it
would be very beneficial to have similar sleep state on the LTE
side, also with an active S1* connection, so that the sleeping UE
can move between NR and LTE without performing signaling to setup
and tear down the S1* connection. This type of inter-RAT
re-selection between LTE and NR may be quite common, especially
during early deployments of NR. Accordingly, a common RAN-based
sleep state called RRC_CONNECTED DORMANT should be introduced in
LTE. The UE behavior in this state is similar to what is defined
for LTE RRC suspend/resume, however the paging is done by the RAN
and not by the CN, since the S1* connection is not torn down when
RRC is suspended.
Similarly, a common RRC_CONNECTED ACTIVE state between NR and LTE
is desirable. This state is characterized in that the NR/LTE
capable UE is active in either NR or LTE or both. Whether the UE is
active in NR or LTE or both is a configuration aspect within the
RRC ACTIVE state, and these conditions need not be regarded as
different sub states, since the UE behavior is similar regardless
which RAT is active. To give one example, in the case only one of
the links is active, regardless of which link, the UE is configured
to transmit data in one and to perform measurements in another one
for dual-connectivity and mobility purposes.
FIG. 3 shows the UE states in an LTE/NR system where LTE supports
the common RRC_CONNECTED ACTIVE and RRC_CONNECTED DORMANT states
discussed above. These states are described further below.
Detached (Non RRC configured)
EMM_DETACHED (or EMM_NULL) state defined in Evolved Packet
Subsystem (EPS) when the UE is turned off or has not yet attached
to the system. In this state the UE does not have any Internet
Protocol (IP) address and is not reachable from the network. Same
EPS state is valid for both NR and LTE accesses. ECM/RRC_IDLE This
is similar to the current ECM_IDLE state in LTE. This state may be
optional. In the event this state is kept, it is desirable for the
paging cycles and Tracking RAN Areas to be aligned between
RAN-based paging in RRC DORMANT and CN-based paging in ECM_IDLE,
since then the UE could listen to both CN- and RAN-based paging
making it possible to recover the UE if the RAN based context is
lost. RRC_CONNECTED ACTIVE (RRC state) UE is RRC-configured, e.g.,
it has one RRC connection, one S1* connection and one RAN context
(including a security context), where these may be valid for both
LTE and NR in the case of dual-radio UEs. In this state it is
possible, depending on UE capabilities, to transmit and receive
data from/to NR or LTE or both (RRC configurable). In this state,
the UE is configured with at least an LTE Serving Cell or an NR
serving beam and can quickly set up dual connectivity between both
NR and LTE when needed. The UE monitors downlink scheduling
channels of at least one RAT and can access the system via for
instance scheduling requests sent in the uplink. Network controlled
beam/node mobility: UE performs neighbouring beam/node measurements
and measurement reports. In NR, the mobility is primarily based on
NR signals such as TSS/MRSs and in LTE, Primary Synchronization
Sequence (PSS)/Secondary Synchronization Sequence (SSS)/CRS is
used. NR/LTE knows the best beam (or best beam set) of the UE and
its best LTE cell(s). The UE may acquire system information via a
Signature Sequence Index (SSI) and corresponding Access Information
Table (AIT), for example, and/or via NR dedicated signaling or via
LTE system information acquisition procedure. UE can be DRX
configured in both LTE and NR to allow micro-sleeps (in NR
sometimes referred as beam tracking or monitoring mode). Most
likely the DRX is coordinated between RATs for UEs active in both
RATs. The UE can be configured to perform measurements on a
non-active RAT which can be used to setup dual connectivity, for
mobility purposes or just use as a fallback if the coverage of the
active RAT is lost. RRC_CONNECTED DORMANT (RRC state) UE is
RRC-configured, e.g., the UE has one RRC connection and one RAN
context regardless of the access. UE can be monitoring NR, LTE, or
both, depending on coverage or configuration. RRC connection
re-activation (to enter RRC ACTIVE) can be either via NR or LTE.
UE-controlled mobility is supported. This can be cell re-selection
in the case of only LTE coverage or NR Tracking RAN Area selection
in the case of NR-only coverage. Alternatively, this can be a
jointly optimized cell/area reselection for overlapping NR/LTE
coverage. UE-specific DRX may be configured by RAN. DRX is largely
used in this state to allow different power saving cycles. The
cycles can be independently configured per RAT, however some
coordination might be required to ensure good battery life and high
paging success rate. Since the NR signals have configurable
periodicity there are methods that allow the UE to identify the
changes and adapt its DRX cycles. UE may acquire system information
via SSI/AIT in NR or via LTE. UE monitors NR common channels (e.g.,
NR paging channel) to detect incoming calls/data, AIT/SSI changes,
Earthquake Tsunami Warning System (ETWS) notification and
Commercial Mobile Alert System (CMAS) notification. UE can request
system information via a previously configured Random Access
channel (RACH).
Several different types of measurements and/or signals are measured
in NR, e.g., MRS, SSIs, Tracking RAN Areas Signals (TRAS), etc.
Mobility events and procedures thus need to be addressed for
NR.
The RRC Connection Reconfiguration message should be able to
configure both the NR measurements and the existing LTE
measurements for the single RRC option. The measurement
configuration should include the possibility to configure the UE to
measure for NR/LTE coverage e.g., to initiate DC setup or inter-RAT
handover (as in the legacy).
There are two different measurement reporting mechanisms for NR,
non-RRC based reporting, where the UE indicates the best of a set
of candidate downlink beams through a preconfigured uplink
synchronization signal (USS) sequence; and RRC-based reporting,
which is similar in some respects to the event-triggered LTE
measurement reporting. These two measurement reporting mechanisms
are preferably deployed in parallel and used selectively, e.g.,
depending on the UE's mobility state.
System information as known from previous releases of the LTE
standards consists of very different types of information, access
information, node-specific information, system-wide information,
public warning system (PWS) information, etc. Delivery of this wide
range of information does not use the same realization in NR. In a
system with high-gain beamforming, the cost of providing large
amount of data in broadcast manner may be costly compared to point
to point distribution in a dedicated beam with high link gain.
The paging solution for NR utilizes one or both of two channels: a
Paging Indication Channel (PICH) and a Paging Message Channel
(PMCH). The paging indication may contain one or more of the
following: a paging flag, warning/alert flag, identifier (ID) list,
and resource allocation. PMCH may optionally be transmitted after
the PICH. When the PMCH message is sent, it may contain one or more
of the following contents: ID list, and warning/alert message.
Warning and broadcast messages are preferably to be transmitted
over the PMCH (and not in the AIT). To allow tight integration with
LTE, paging configuration (and so DRX configuration) may be
Single-Frequency Network (SFN)-based.
To support paging functionality, tracking RAN areas are configured
at the UE. A tracking RAN area (TRA) is defined by a set of nodes
transmitting the same tracking RAN area signal (TRAS). This signal
contains the Tracking RAN Area Code as well as the SFN.
Each TRA may have a specific paging and TRAS configuration which is
provided to the UE via dedicated signaling, e.g., via a TRA Update
Response or RRC Reconfiguration message. The TRA Update Response
may, furthermore, contain paging messages.
A number of different reference signals are provided in NR, for
channel estimation and mobility. Both the presence of the reference
signals as well as the measurement reports are controlled by the
scheduler. The presence of signals can be dynamically or
semi-persistently signaled to one or a group of users.
Also, reference signals for active mode mobility (MRS) can be
dynamically scheduled. A UE is then assigned with a search space
for mobility transmissions. Observe that this search space is
potentially monitored by one or more UEs and/or transmitted from
one or more transmission points.
Scheduled reference signal transmissions (such as MRS) contain a
locally unique (at least within the search space) measurement
identity in the data message, and reuse some or multiple of the
pilots in the transmission both for demodulation and measurement
purposes, implying that it is a self-contained message.
NR uses OFDM as modulation scheme in both uplink and downlink,
possibly also including a low peak-to-average power ratio (PAPR)
mode (e.g., discrete Fourier transform-spread OFDM, or DFTS-OFDM)
for energy-efficient low-PAPR operation and Filtered/Windowed OFDM
for frequency-domain mixing of numerologies. Note that a
"numerology," as that term is used herein, refers to a particular
combination of OFDM subcarrier bandwidth, cyclic prefix length, and
subframe length. The term subcarrier bandwidth, which refers to the
bandwidth occupied by a single subcarrier, is directly related to,
and is sometimes used interchangeably, with subcarrier spacing.
The modulation scheme of NR is cyclic-prefix OFDM, both for uplink
and downlink, which enables a more symmetric link design. Given the
large operating range of NR, sub-1 GHz to 100 GHz, multiple
numerologies may be supported for the different frequency regions.
OFDM is a good choice for NR, since it combines very favorably with
multi-antenna schemes, another significant component in NR. In
OFDM, each symbol block is very well localized in time, which makes
OFDM also very attractive for short transmission bursts, important
for various MTC applications. OFDM does not provide as good
isolation between subcarriers as some filter-bank based schemes do;
however, windowing or sub band filtering provide sufficient
isolation between sub bands (e.g., not individual subcarriers but
collections of subcarriers), where needed.
For some use-cases, mixing of different OFDM numerologies is
beneficial. Mixing of OFDM numerologies can either be done in
time-domain or frequency domain. For mixing of MBB data and
extremely latency-critical MTC data on the same carrier,
frequency-domain mixing of OFDM numerologies is beneficial.
Frequency-domain mixing can be implemented using Filtered/Windowed
OFDM. FIG. 4(a) shows a block diagram of Filtered/Windowed OFDM. In
this example, the upper branch uses narrow (16.875 kHz) subcarriers
400-1100. The lower branch uses wide (67.5 kHz) subcarriers 280-410
which correspond to narrow subcarriers 1120-1640. FIG. 4(b) shows
the mapping of upper and lower branches to the time-frequency
plane. During the time duration of the large Inverse Fast Fourier
Transform (IFFT) (2048 samples), four small IFFTs (512 samples) are
performed.
In Filtered OFDM, sub bands are filtered to reduce interference
towards other sub bands. In Windowed OFDM, beginning and end of
OFDM symbols are multiplied with a smooth time-domain window
(regular OFDM uses a rectangular window spanning the length of an
OFDM symbol including cyclic prefix) reducing discontinuities at
symbol transitions and thus improve spectrum roll off. This is
shown in FIG. 5, which illustrates how the beginning and end of an
OFDM symbol are multiplied by a smooth time-domain window.
In the example frequency-domain mixing of OFDM numerologies shown
in FIG. 4, the lower branch uses numerology with four times as wide
subcarriers as the upper branch, e.g., 16.875 kHz and 67.5 kHz for
the upper and lower branch, respectively. In this example, both
branches use the same clock rate after IFFT processing and can
directly be added. However, in a practical realization this may not
be the case; especially if one of the numerologies spans a much
narrower bandwidth than the other processing at a lower sampling
rate is preferable.
While filtered OFDM is possible, windowed OFDM is preferred due to
its greater flexibility.
Sub band filtering or windowing (both at the transmitter and the
receiver) and guard bands are desirable to suppress
inter-subcarrier interference, since subcarriers of different
numerologies are not orthogonal to each other. In addition to sub
band filtering or windowing, filtering across the transmission
bandwidth is also desirable, to fulfill the desired out-of-band
emission requirements. A guard band of 12 narrowband subcarriers
enables an SNR of 20+ dB on all subcarriers, while a guard band of
72 narrowband subcarriers allows an SNR of 35+ dB on all
subcarriers. To avoid unnecessary guard band losses,
Filtered/Windowed OFDM may be limited to two contiguous blocks of
different numerologies. To the extent that Filtered/Windowed OFDM
is supported by the NR standard, every NR device--even a device
only supporting a single numerology--should support transmit and
receive filtering/windowing since it could operate on an NR carrier
operating with mixed numerologies (given the low complexity of
windowing it is reasonable to assume that every UE can implement
windowing). A network node on the other hand, needs only to support
Filtered/Windowed OFDM if it supports use case mixes requiring
frequency-domain mixing of numerologies. Note that detailed
specifications of the windowing or sub band filtering are not
needed, but rather performance requirements to test the chosen
implementation. Sub band filtering and windowing can also be mixed
on transmitter and receiver.
OFDM may also include a low-PAPR mode such as DFTS-OFDM. OFDM is
used to maximize performance while the low-PAPR mode might be used
in node realizations (both eNB and UE) where low peak to average
power ratio (PAPR) of the waveform is important from a hardware
perspective, e.g., at very high frequencies.
At the physical layer, the minimum transmission unit is a subframe.
Longer transmissions can be realized by subframe aggregation. This
concept enables a variable TTI, for a given transmission the TTI
corresponds to the length of the subframe or to the length of the
subframe aggregate in case of subframe aggregation.
Three subcarrier bandwidths are defined to cover the operating
range from below 1 GHz to 100 GHz and the large use case space.
NR supports both frequency-division duplexing (FDD) and dynamic
time-division duplexing (TDD) modes. Even though not relevant for
the first releases of NR, the concept is extendable to full duplex,
especially at the base station, as full duplex technology becomes
more mature.
The NR physical layer as described herein has no frames but only
subframes. It is possible that the concept of frames can be
introduced later. Two basic subframe types, one for uplink and one
for downlink, are defined. These subframe types are identical for
both FDD and TDD. FIG. 6 depicts the basic subframe types, where
T.sub.sf is the subframe duration. T.sub.DL and T.sub.UL are the
active transmission durations in downlink and uplink, respectively.
A subframe consists of N.sub.symb OFDM symbols, but not all symbols
in a subframe are always used for active transmission. Transmission
in a downlink subframe starts at the beginning of the subframe and
can extend from 0 up to at most N.sub.symb OFDM symbols (later
start of a transmission in a downlink subframe for
listen-before-talk operation is also possible). Transmission in an
uplink subframe stops at the end of the subframe and can extend
from 0 up to at most N.sub.symb OFDM symbols. The gaps--if
present--are used in TDD for transmission in the reverse direction
within a subframe, as explained below.
The duration of a single subframe is very short. Depending on the
numerology, the duration may be a few hundred .mu.s or even less
than 100 .mu.s, in the extreme case even less than 10 .mu.s. Very
short subframes are important for Critical Machine-Type
Communication (C-MTC) devices requiring short latency, and such
devices typically check for control signaling transmitted at the
beginning of every downlink subframe. Given the latency critical
nature, the transmission itself can also be very short, e.g., a
single subframe.
For MBB devices, extremely short subframes are typically not
needed. It is therefore possible to aggregate multiple subframes
and schedule the subframe aggregate using a single control
channel.
It is well known that robustness of an OFDM system towards phase
noise and Doppler shift increases with subcarrier bandwidth.
However, wider subcarriers imply shorter symbol durations
which--together with a constant cyclic prefix length per
symbol--result in higher overhead. The cyclic prefix should match
the delay spread and is thus given by the deployment. The required
cyclic prefix (in .mu.s) is independent of the subcarrier
bandwidth. The "ideal" subcarrier bandwidth keeps the cyclic prefix
overhead as low as possible but is wide enough to provide
sufficient robustness towards Doppler and phase noise. Since the
effect of both Doppler and phase noise increase with carrier
frequency the required subcarrier bandwidth in an OFDM system
increases with higher carrier frequency.
Considering the wide operating range of below 1 GHz to 100 GHz it
is impossible to use the same subcarrier bandwidth for the complete
frequency range and keep a reasonable overhead. Instead, three
subcarrier bandwidths span the carrier frequency range from below 1
to 100 GHz.
To enable subframe durations of a few 100 .mu.s using LTE
numerology (for LTE frequencies), one subframe would have to be
defined as a few OFDM symbols. However, in LTE, OFDM symbol
durations including cyclic prefix vary (the first OFDM symbol in a
slot has a slightly larger cyclic prefix) which would lead to
varying subframe durations. (Varying subframe durations are in
practice likely not a significant problem and could be handled. In
LTE, the varying cyclic prefix length leads to somewhat more
complicated frequency error estimators.) Alternatively, a subframe
could be defined as an LTE slot, leading to subframe durations of
500 .mu.s. This, however is considered too long.
Therefore, even for LTE frequencies a new numerology is described
herein. The numerology is close to the LTE numerology, to enable
the same deployments as LTE, but provides subframes of 250 .mu.s.
The subcarrier bandwidth is 16.875 kHz. Based on this subcarrier
bandwidth several other numerologies are derived: 67.5 kHz for
around 6 to 30/40 GHz or dense deployments (even at lower
frequencies) and 540 kHz for the very high frequencies. Table 1
lists the most important parameters of these numerologies, e.g.,
f.sub.s: Clock frequency, N.sub.symb: OFDM symbols per subframe,
N.sub.sf: samples per subframe, N.sub.ofdm: Fast Fourier Transform
(FFT) size, N.sub.cp: cyclic prefix length in samples, T.sub.sf:
subframe duration, T.sub.ofdm: OFDM symbol duration (excluding
cyclic prefix), and T.sub.cp: cyclic prefix duration). Table 1 is
based on an FFT size of 4096 and a clock frequency of 34.56 MHz to
allow the covering of large carrier bandwidths.
The proposed numerologies are not based on the LTE clock frequency
(30.72 MHz) but on 16.875/1530.72 MHz=9/830.72 MHz=93.84 MHz=34.56
MHz. This new clock relates via a (fractional) integer relation to
both LTE and Wideband Code-Division Multiple-Access (WCDMA) clocks
and can thus be derived from them.
TABLE-US-00001 TABLE 1 Subcarrier bandwidth 16.875 kHz, normal
cyclic prefix 16.875 kHz, 67.5 kHz, 67.5 kHz, long 540 kHz, (CP)
long CP normal CP CP normal CP Main scenario <~6 GHz <~6 GHz
~6 to 30-40 GHz Low delay in >30-40 GHz SFN or wide-area transm.
dense depl. deployments f.sub.s in MHz 69.12 = 2 .times. 34.56
276.48 = 2 .times. 138.24 2212 = 2 .times. 1105.92 N.sub.symb 4 3 4
7 4 (larger number is possible) N.sub.sf 17280 17280 17280 34560
17280 N.sub.ofdm 4096 4096 4096 4096 4096 N.sub.cp 224 1664 224 4
.times. 848, 3 .times. 832 224 CP overhead in % 5.5 40.6 5.5 20.5
5.5 T.sub.sf in .mu.s 250 250 62.5 125 7.81 T.sub.ofdm in .mu.s
59.26 59.26 14.82 14.82 1.85 T.sub.cp in .mu.s 3.24 24.07 0.81 3.01
0.10 T.sub.ofdm + T.sub.cp in 62.5 83.33 15.625 17.86 1.95 .mu.s
Max carrier 60 60 250 250 2000 band- width in MHz
Note that numerologies for implementations may vary from those
listed in Table 1. In particular, numerologies with long cyclic
prefixes may be adjusted.
Table 1 shows that OFDM symbol duration and subframe duration
decrease with subcarrier bandwidth, making numerologies with wider
subcarriers suitable for low-latency application. The cyclic prefix
length also decreases with subcarrier bandwidth, limiting the wider
subcarrier configurations to dense deployments. This can be
compensated by long cyclic prefix configuration, at the price of
increased overhead. In other words, shorter subframes and thus
latencies are more efficiently available in small cells than in
large cells. In practice, however, it is expected that many latency
critical applications deployed in the wide area (and thus require a
cyclic prefix larger than 1 .mu.s) don't require subframe durations
smaller than 250 .mu.s. In the rare cases where wide area
deployments require smaller subframe durations, 67.5 kHz subcarrier
bandwidth--with long cyclic prefix if needed--can be used. The 540
kHz numerology provides even shorter subframes.
The maximum channel bandwidths of the different numerologies are,
approximately, 60 MHz, 240 MHz, and 2 GHz for 16.875 kHz, 67.5 kHz,
and 540 kHz numerology, respectively (assuming an FFT size of
4096). Wider bandwidths can be achieved with carrier
aggregation.
Mixing of different numerologies on the same carrier is possible,
using Filtered/Windowed OFDM. One of the motivations is to achieve
lower latency on a part of the carrier. Mixing of numerologies on a
TDD carrier should obey the half-duplex nature of TDD--simultaneous
transmission and reception capability of a transceiver cannot be
assumed. The most frequent duplex switching in TDD is thus limited
by the "slowest" numerology among the simultaneously used ones. One
possibility is to enable duplex switching on the "fastest"
numerology subframe basis when needed and accept losing currently
ongoing transmission in the reverse link.
Signature sequences (SS), as discussed below, are used to indicate
an entry in AIT and to establish some level of subframe
synchronization for at least random access preamble transmission.
SS are constructed in a similar way as the synchronization signal
in LTE by concatenation of a primary signature sequence and a
secondary signature sequence.
The combination of time and frequency synchronization signal (TSS)
and beam reference signal (BRS) is used to obtain
time/frequency/beam synchronization after initial synchronization
and access by SS and Physical Random Access Channel (PRACH). This
combined signal is also referred to as MRS (mobility reference
signal) and is used for handover (between nodes and beams),
transitions from dormant to active states (e.g., from RRC_CONNECTED
DORMANT to RRC_CONNECTED ACTIVE, as discussed above), mobility,
beam tracking and refinement, etc.
The MRS is constructed by concatenating TSS and BRS such that MRS
is transmitted within a single DFT-precoded OFDM symbol.
Channel state information reference signals (CSI-RS) are
transmitted in downlink and are primarily intended to be used by
UEs to acquire channel state information (CSI). CSI-RS are grouped
into sub-groups according to the possible reporting rank of the UE
measurement. Each sub-group of CSI-RS represents a set of
orthogonal reference signals.
Positioning reference signals (PRS) aid positioning. Already
existing reference signals should be reused for PRS purposes. On
top of that--if required--modifications and additions can be done
to improve positioning performance.
TABLE-US-00002 TABLE 2 Downlink reference and synchronization
signals in NR Signal Purpose Signature sequence (SS) Used to
synchronize time and frequency for random access. Provides index to
AIT table. Mobility and access reference Concatenation of one TSS
and one BRS Signal (MRS) Time and frequency Used to synchronize
time (OFDM symbol timing) and coarse synchronization signal (TSS)
frequency offset estimation in a beam. Beam reference signal (BRS)
Used for measurements on beam candidates to enable active mode
mobility. Also used for frame and subframe timing. Demodulation
reference signal Demodulation reference signals for PDCCH (DMRS)
for PDCCH Channel state information Used for channel state
measurements to aid rank and reference signal (CSI-RS) Modulation
and Coding Scheme (MCS) selection. Positioning reference signal To
aid positioning. (PRS)
Basic functions of the signature sequence (SS) are one or more of:
to obtain the SSI, which is used to identify the relevant entry in
AIT; to provide coarse frequency and time synchronizations for the
following initial random access and relative AIT allocation; to
provide a reference signal for initial layer selection (to select
which SS transmission point for a UE to connect, based on the
path-loss experienced by SS's); to provide a reference signal for
open-loop power control of the initial PRACH transmission; and to
provide a coarse timing reference used for assisting the UE in
inter-frequency measurements and also possible beam finding
procedure. The current assumption is that SS transmissions are
synchronized within a .+-.5 ms uncertainty window unless explicitly
indicated otherwise. The period of SS is supposed to be in the
order of 100 ms, which however may be varied, depending on the
scenarios.
It is noted that the number of the candidate sequences needs to be
large enough to indicate any entry in AIT. Taking the terminal
detection complexity into account, the number of SS sequences is
2.sup.12, corresponding to 12 bits for reuse 1 of the sequences, or
less if less aggressive sequence reuse is required. Note that the
number of bits to be carried depends on requirements. If the number
of bits increases beyond what can be carried by sequence
modulation, a variation of the SS format is desirable. In this
case, one code-word containing the extra bits beyond what the
sequences can carry can be appended. This block, following an SS
transmission, is named SS block (SSB). The content in this block is
flexible and contains the other relevant information bits, which
need a periodicity in the order of 100 ms. For example, they can be
the "AIT pointer", which indicates the time and band where the
terminals can find the AIT and even the transmission format of AIT
to avoid full blind detection.
The sequence design for SS can follow the TSS/BRS sequence design,
since they would provide the coarse synchronization function before
the initial random access.
To support the massive analog beamforming, a fixed absolute time
duration, e.g., 1 millisecond, is reserved to sweep multiple analog
beams.
In the process of acquiring system access information (acquiring
system information and detecting a suitable SSI), the UE gets time
and frequency synchronized towards one or several nodes by using
SS. The latter is achieved in the case of system access information
transmitted simultaneously from several nodes in an SFN (single
frequency network) manner.
When the UE enters active mode, it targets to receive or transmit
with a high data rate connection, in which it might need more
accurate synchronization and perhaps beamforming.
Here, the mobility and access reference signal (MRS) is used. A UE
might also need to change which node it is connected to e.g., from
a node used to transmit system access information to another node
capable of beamforming. Furthermore, the UE might also change
carrier frequency or numerology to higher sub-carrier spacing and
shorter cyclic prefix when moving to certain operational modes in
active mode.
The MRS is constructed in order to do time and frequency offset
estimations as well as estimation of best downlink transmitter and
receiver beams towards an "active mode access point". Frequency
accuracy and timing provided by MRS is probably not sufficient for
high-order modulation reception and finer estimation may be based
on demodulation reference signals (DMRS) embedded in Physical Data
Channel (PDCH) and/or CSI-RS.
The MRS may be constructed by concatenating a time and frequency
synchronization signal (TSS) and a beam reference signal (BRS) in
time into one OFDM symbol, as illustrated in FIG. 7. This
construction can be done as a DFT-precoded OFDM symbol with cyclic
prefix. With both TSS and BRS in the same OFDM symbol, the
transmitter can change its beamforming between each OFDM symbol.
Compared to having separate OFDM symbols for TSS and BRS, the time
required for scanning a set of beam directions is now halved. Both
TSS and BRS thus have shorter time durations as compared to
separate OFDM symbols for each of them. The cost for these shorter
TSS and BRS is reduced energy per signal and thus reduced coverage,
which can be compensated by increasing the bandwidth allocation,
repeating the signal, or increasing the beamforming gain by more
narrow beams. Where mixed numerology is supported, the numerology
used for MRS is the same as that one used by the UE for which MRS
are scheduled. In the event that multiple UEs within the same beam
use different numerologies, MRS cannot be shared and MRS should be
transmitted separately for each numerology.
Different beamforming configurations can be used to transmit the
MRS in different OFDM symbol, e.g., in each of the three symbols
shown in FIG. 7. The same MRS might also be repeated several times
in the same beam in order to support analog receiver beamforming.
There are only one or few TSS sequences, similar to PSS in LTE. The
UE performs matched filtering with the TSS sequence to obtain OFDM
symbol timing estimation; TSS should therefore possess good
a-periodic auto-correlation properties. This sequence might be
signaled by system information such that different AP (Access
Points) can use different TSS sequences.
The MRS (as constructed by TSS+BRS) signal package is usable for
all active mode mobility-related operations: first-time beam
finding, triggered beam mobility update in data transmission and
monitoring modes, and continuous mobility beam tracking. It may
also be used for the SS design.
The TSS sequence is identical in all OFDM symbols and beam
directions transmitted from a base station, while BRS uses
different sequences in different OFDM symbols and beam directions.
The reason for having identical TSS in all symbols is to reduce the
number of TSS which a UE must search in the quite computational
complex OFDM symbol synchronization. When the timing is found from
TSS, the UE can continue to search within a set of BRS candidates
in order to identify the OFDM symbol within a subframe as well as
best downlink beam. Best downlink beam can then be reported by
USS.
One choice for such sequences is the Zadoff-Chu sequences as used
for PSS in LTE release 8. However, these sequences are known to
have large false correlation peaks for combined timing and
frequency offsets. Another choice is differential coded Golay
sequences, which are very robust against frequency errors and have
small false correlation peaks.
The beam reference signal (BRS) is characterized by different
sequences transmitted in different transmitted beams and OFDM
symbols. In this way, a beam identity can be estimated in the UE
for reporting to the access node.
An identification of OFDM symbol within the subframe is desirable
if the timing difference between SS and active mode transmissions
is large. This might occur for numerologies with short OFDM
symbols, large distance between the node transmitting system access
information and the node in which the UE is supposed to transmit
user data (in case these nodes are different), or for
unsynchronized networks. This identification can be done if
different BRS sequences are used for different OFDM symbols.
However, in order to reduce computational complexity, the number of
BRS sequences to search for should be low. Depending on the OFDM
symbol index uncertainty, a different number of BRS sequences may
be considered in the blind detection of the UE.
The BRS can be a dedicated transmission to one UE or the same BRS
might be configured for a group of UEs. A channel estimate from TSS
can be used in a coherent detection of BRS.
CSI-RS are transmitted in downlink and are primarily intended to be
used by UEs to acquire channel state information (CSI) but can also
serve other purposes. The CSI-RS may be used for one or more of (at
least) the following purposes: Effective channel estimation at the
UE: Frequency selective CSI acquisition at the UE within a downlink
beam, e.g., used for Precoder Matrix Indicator (PMI) and rank
reporting. Discovery signal: Reference Signal Receive Power
(RSRP)-type measurement on a set of CSI-RS reference signals.
Transmitted with a time density according to large scale coherence
time of the relevant (downlink) channels. Beam refinement and
tracking: Get statistics about the downlink channel and PMI
reporting to support beam refinement and tracking. PMI does not
need to be frequency selective. Transmitted with a time density
according to large scale coherence time of the relevant (downlink)
channels. For UE transmit beam-forming in uplink assuming
reciprocity. UE beam-scanning for analog receive beam-forming in
downlink (similar requirements to 1) or 3) depending on use-case).
To assist fine frequency/time-synchronization for demodulation.
In some cases, not all of the above estimation purposes needs to be
handled by CSI-RS. For example, frequency offset estimation can
sometimes be handled by downlink-DMRS, beam-discovery is sometimes
handled by BRS. Each CSI-RS transmission is scheduled and can be in
the same frequency resources as a PDCH downlink-transmission or in
frequency resources unrelated to the PDCH downlink-data
transmissions. In general, no interdependence between CSI-RS in
different transmissions can be assumed, and hence the UE should not
do filtering in time. However, a UE can be explicitly or implicitly
configured to assume interdependence between CSI-RS, for example,
to support time-filtering of CSI-RS measurements (e.g., in 2 above)
and also interdependence to other transmissions including PDCCH and
PDCH. In general, all UE filtering shall be controlled by the
network, including filtering of CSI in time, frequency and over
diversity branches. In some transmission formats, CSI-RS is
situated in a separate OFDM symbol to better support analog
beam-forming both for the base station transmitter (TX) and the UE
receiver (RX). For example, to support UE analog beam-scanning
(item 5 above) the UE needs multiple CSI-RS transmissions to
measure on in order to scan multiple analog-beam candidates.
In LTE, the UE camps in a "cell". Prior to camping, the UE performs
a cell selection which is based on measurements. Camping means that
the UE tunes to the cell control channels and all the services are
provided from a concrete cell and the UE monitors the control
channels of a specific cell.
In NR, different nodes may transmit different information. Some
nodes may transmit the SSI/AIT table, while others may not transmit
SSI and/or AIT, for instance. Similarly, some nodes could transmit
the tracking information while others may transmit paging messages.
The notion of cell becomes blurry in this context and, therefore,
the concept of cell camping is no longer suitable in NR.
The relevant signals the UE may monitor while in a dormant state or
mode (e.g., the RRC_CONNECTED DORMANT state discussed above) are
one or more of: SSI Tracking RAN Area Signal--TRAS Paging
Indication Channel/Paging Message Channel.
NR camping is, therefore, related to the reception of a set of
signals. The UE should camp on the "best" SSI, TRAS, and PICH/PMCH.
NR camping (re-)selection rules for these signals are used, just as
cell (re-)selection rules exist in LTE. However, since the degree
of flexibility is higher, these rules may also be slightly more
complicated.
Location information is desirable to assist the network to locate
the UE. Solutions to provide location information using the SSI/AIT
are possible; however, at the cost of introducing certain
constraints. Another solution is to use the SSI block. The SSI
block could carry the content or part of the content described in
the Tracking RAN Area Signal Index (TRASI). The SSI block is
independent of the SSI. Therefore, it could qualify as an option to
provide location information. Yet, another solution which provides
a higher degree of flexibility is to introduce a new signal to
carry such information. This signal is in this context called
Tracking RAN Area Signal, TRAS. The area in which this signal is
transmitted is called Tracking RAN Area, TRA. A TRA may contain one
or more RAN nodes, as depicted in FIG. 8. The TRAS may be
transmitted by all or a limited set of nodes within the TRA. This
also means that this signal and its configuration should preferably
be common for all the nodes transmitting the TRAS within the given
TRA, e.g., in terms of (at least) roughly synchronized
transmissions, to facilitate the procedures for the UE and aid it
to reduce its energy consumption.
The Tracking RAN Area Signal (TRAS) comprises two components, a
Tracking RAN Area Signal Synchronization (TRASS) and a Tracking RAN
Area Signal Index (TRASI).
In dormant mode, prior to each instance of reading the TRA info,
the UEs are typically in a low-power DRX state and exhibit a
considerable timing and frequency uncertainty. The TRA signal
should therefore also be associated with a sync field that allows
the UE to obtain timing and frequency synchronization for
subsequent payload reception. To avoid duplicating synchronization
support overhead in yet another signal, TRASI reception can use SSI
for the purposes of synchronization in deployments where SSI and
TRAS are transmitted from same nodes and are configured with a
suitable period. In other deployments where the SSI is not
available for sync prior to reading TRASI, a separate sync signal
(TRASS) is introduced for that purpose.
The SSI design has been optimized to provide UE synchronization.
Since the synch requirements for TRA detection, not least the link
quality operating point for the UE and the required ability to read
the downlink payload information, are similar, we reuse the SS
physical channel design and reserve one, or a small number, of the
PSS+SSS sequence combinations to be used as the TRA sync signal.
The SS detection procedure at the UE may be reused for TRA
synchronization. Since TRASS constitutes a single predetermined
sequence, or a small number of them, the UE search complexity is
reduced.
Information about whether TRASS is configured by the network may be
signaled to the UE, or the UE may detect it blindly.
The tracking area index is broadcasted. At least two components
have been identified to be included in the Tracking RAN Area Signal
Index (TRASI) payload: Tracking RAN Area code. In LTE, a Tracking
Area code has 16 bits. The same space range may be used for NR.
Timing information. As an example, a System Frame Number (SFN)
length of 16 bits may be used, which would allow a 10 minutes DRX,
given a radio frame length of 10 ms.
The payload is thus estimated as 20-40 bits. Since this number of
bits is impractical to encode into individual signature sequences,
the TRA information is transmitted as coded information payload
(TRASI) with associated reference symbols (TRASS) to be used as
phase reference.
The TRASI payload is transmitted using the downlink physical
channel structure: Alternative 1 [preferred]: Use PDCCH (persistent
scheduling). The UE is configured with a set of 1 or more PDCCH
resources to monitor Alternative 2: Use PDCH (persistent
scheduling). The UE is configured with a set of 1 or more PDCH
resources to monitor Alternative 3: Use PDCCH+PDCH (standard shared
channel access). The UE is configured with a set of 1 or more
Paging Control Channel (PCCH) resources to monitor, which in turn
contain a pointer to PDCH with the TRA info
The choice between PDCCH and PDCH should be based on whether
reserving resources in one or the other channel imposes fewer
scheduling limitations for other signals. (For nomenclature
purposes, the used PDCCH/PDCH resources may be renamed as TRASI
physical or logical channel.
TRASI encoding includes a Cyclic Redundancy Check (CRC) to reliably
detect the correct decoding at the UE.
The UE uses its standard SSI search/sync procedure to obtain sync
for TRASI reception. The following sequence may be used to minimize
the UE energy consumption: First look for TRASS If TRASS not found,
look for most recent SSI If same SSI not found, continue to full
SSI search
In some UE implementations, the receiver wake-up time, i.e., the
periods of time in which all or substantial parts of the receiver
circuitry are activated, is the dominant energy consumption factor,
in which case full search may always be performed.
If no TRASS is present but several SSIs are audible, the UE
attempts TRASI reception at all found SSI and/or TRASS timings, one
of which succeeds. All SSIs are detected and corresponding TRASI
detection is attempted during the same awake period, so no receiver
overhead is introduced.
If a relatively loose sync with a known tolerance within a TRA is
provided, a UE searches for TRAS-related time sync in the relevant
vicinity of the current timing, plus the worst-case timing drift
during the DRX. The UE RX waking time thus increases proportionally
with increased timing tolerance.
TRA configuration should be identical within the TRA. This means
that all the nodes which transmit the TRAS should use the same
configuration. The reason behind this is due to the DRX
configuration. A UE in dormant mode, such as the RRC_CONNECTED
DORMANT state discussed above, wakes up for a certain period of
time. In that period of time, the UE is expected to monitor and
perform measurements as configured by the network (or as mandated
by the standard).
TRA configuration is conveyed via dedicated signaling. AIT is not
the most suitable option to convey this information. The TRA
configuration could be transmitted to the UE, for example, when the
network commands the UE to move from an active Mode, such as
RRC_CONNECTED ACTIVE state to a dormant mode, such as RRC_CONNECTED
DORMANT state, or when the network transmits a TRA Update Response
to the UE. TRA Update Response--could also carry paging information
(see FIG. 9). This could be especially useful to minimize paging
delays in situations when the network is trying to locate a UE in
TRA which the UE has already exited. To be able to support this
type of functionality, the UE may need to add in the TRA Update
some type of ID or other information to assist the new TRA or node
to identify previous TRAs or nodes which could contain the UE
context, paging messages or user data.
In FIG. 9, which illustrates a TRA update procedure, a UE moves
from a TRA_A to a TRA_B which is not configured in its TRA list.
When the UE has exited the TRA_A, but not registered yet in TRA_B,
the network starts sending paging indications over a certain node
or set of nodes in TRA_A. The UE does not respond since it has
exited the TRA_A and may not monitor the TRAS_A any longer. When
the UE performs a TRA Update, the network provides the new TRA list
and configuration, and may further include any paging indications
which the UE could have been missed.
The less synchronized the network is, the higher the UE battery
impact is. Keeping a tight synchronization across TRAs is therefore
important but also challenging, especially in deployments with poor
backhaul.
A few options are listed below: All TRAs are loosely synchronized.
No synchronization across TRASs. Sliding synchronization across
neighbour nodes. Loosely synchronized within the TRA & not
synchronization among TRASs.
FIG. 10 illustrates options of beam shapes for feedback-based
solutions in NR.
Transmitting in a beam implies that there is a directional,
possibly narrow, propagating stream of energy. The notion of a beam
is thus closely related to the spatial characteristics of the
transmission. To ease the discussion, the beam concept is first
explained. In particular, the notion of a high-rank beam is
described.
Here, a beam is defined as a set of beam weight vectors, where each
beam weight vector has a separate antenna port, and all the antenna
ports have similar average spatial characteristics. All antenna
ports of a beam thus cover the same geographical area. Note,
however, that the fast fading characteristics of different antenna
ports may be different. One antenna port is then mapped to one or
several antenna elements, using a possibly dynamic mapping. The
number of antenna ports of a beam is the rank of the beam.
To illustrate the beam definition, take the most common example of
a rank-2 beam. Such a beam is realized using an antenna with
cross-polarized elements, where all antenna elements with one
polarization are combined using one beam weight vector, and all
antenna elements with the other polarization are combined using the
same beam weight vector. Each beam weight vector has one antenna
port, and since the same beam weight vector is used for the two
antenna ports, the two beam weight vectors together constitute one
rank-2 beam. This can then be extended to beams of higher rank.
Note that high-rank beams may not work for the UE. Due to the
irregular antenna element layout, the rich scattering at the UE and
the fact that the UE antenna elements may have different
characteristics, it is very challenging to construct several beam
weight vectors with similar spatial characteristics. Note that this
does not preclude spatial multiplexing in the uplink: this can be
achieved using several rank-1 beams.
It is very important to note that the beam shapes can be quite
flexible. Hence, "beam-based transmission" is not the same as
"fixed-beam transmission", although using a fixed grid of beams may
be a suitable implementation in many cases. The working assumption
is that each beam has between 1 and 8 ports, and each beam is
associated with a CSI-RS with a rank ranging from 1 to 8.
From UE's point of view, no major difference to element-based
feedback is foreseen other than the CSI-RS configuration; namely,
that for beam-based transmission, the CSI-RS allocations need to be
more flexible. Even though the configuration is flexible this does
not preclude that the UE may do filtering and interpolation, but
this is under strict network control.
In beam-based transmission, communication occurs through beams,
where the number of beams may be much smaller than the number of
antenna elements. Since the beams are still adjustable, the antenna
system as a whole retains all its degrees of freedom. However, a
single UE is not capable of supporting all these of freedom using
instantaneous feedback. Note that this is in contrast to
element-based transmission, where the UE sees all the degrees of
freedom of the antenna, and is capable of reporting based on this
knowledge.
From the network's point of view, multiple simultaneous beams can
be generated, either using analog beamforming or digital domain
processing. It is assumed that as long as the formed beams are of
similar width as the angular spread of the channel, the overhead to
maintain the UE beam associations are reasonable: the best beam for
any single UE does not then vary with the fast fading. When the
beam is narrower than the angular spread of the channel, the best
beam for any single UE varies over time, leading to that the best
beam association needs to be frequently updated. In some cases, the
antenna patterns are fixed; see FIG. 10, option 2. In some cases,
the beams are adapted to the UEs channel characteristics; see FIG.
10, option 3, where user 2 with a rich channel receives data
through a wide high-rank beam and the line-of-sight user 1 a narrow
rank-2 beam.
Beam-based transmission is applicable in both FDD and TDD, for any
frequency band, and antenna size.
Beam-based uplink reception implies that the baseband does not have
individual access to all antenna elements. In this case, some sort
of spatial preprocessing or preliminary beamforming may be applied.
This preprocessing can be performed in the analog domain, in the
digital domain, or in a hybrid of the two. In general, the spatial
preprocessing can be quite flexible. It needs to be time-varying to
adapt the coverage area of the antenna to where the users are.
Both phase and amplitude tapering can be considered.
In the downlink, the individual antenna elements are never exposed
to the UE. The UE only sees a number of linear combinations of the
signals transmitted from different antenna elements. The number of
linear combinations that is exposed is determined by the rank of
the transmission. Data is received at the UE through such a linear
combination (the beam) and downlink quality is measured and
reported per beam.
One possible scenario is that the UE is equipped with multiple
arrays, each array consisting of a (small) number of elements. The
different arrays cover different spatial directions. The array can
be configured to have different angular coverage (pointing
direction and beam width).
The UE transmits reference signals (RSs) through a number of beams,
either sequentially or simultaneously. Sequential transmission can
be used also with analog TX beamforming, and the detection at the
eNB is easier. On the other hand, if RSs are transmitted over
several beams in parallel, more beams can be probed in a shorter
time. The RS is probably Reciprocity Refernce Signal (RRS), as
different RSs should be transmitted through different beams, so
that the eNB can identify each transmission. The shape of each beam
is decided by the UE, but the number of beams is between the UE and
the eNB. The eNB measures the quality of each received RS, and
determines the most suitable UE transmit beam. The decision is then
sent to the UE over dPDCH, together with a channel quality
information (CQI) value and a scheduling grant.
As mentioned above, it may not be possible to form a high-rank beam
at the UE. To enable uplink multiple-input multiple-output (MIMO),
several rank-1 beams may be used.
At the eNB, beam-based transmission typically means that the number
of elements seen by the baseband is much lower than the number of
elements used to form the beams. This implies that the (angular)
coverage of simultaneous individual beams is less than by the
elements.
At the UE, beam-based transmission for feedback purposes may be
used to improve link budget for RSs but perhaps not to reduce the
angular coverage, such that the number of beams may still be equal
to the number of elements.
For an ongoing transmission, there is a possibility to reduce the
angular coverage, as is done on the eNB side, but this may imply
that, after some time, the channel is not fully utilized. To
prevent this, sounding, with wide or possibly full angular
coverage, is required.
For NR, the active mobility management solution described above is
configured to manage mobility between beams, as opposed to the
traditional cell mobility in Long-Term Evolution (LTE).
Beam-oriented transmission and mobility introduce numerous features
that differ from LTE cell mobility. Using large planar antenna
arrays at access nodes, with the number of elements in the
hundreds, fairly regular grid-of-beams coverage patterns with
hundreds of candidate beams per node may be created. The beam
widths of the individual beams in elevation and azimuth are
determined by the number of element rows and columns in the
array.
As illustrated in simulation studies, the coverage area of an
individual beam from a large planar array may be small, down to the
order of some tens of meters in width. Channel quality degradation
outside the current serving beam area is rapid, which may
necessitate frequent beam switching to reap the full potential of
the antenna array with low overhead. Static mobility signals in all
beams are not feasible, so MRS need to be turned on only in
relevant beams and only when needed. The relevant beams are
selected based on the UE position and prior beam coverage
statistics for the different candidate beams, based on a
self-organizing network (SON) database. The SON data may also be
used to trigger mobility measurement sessions when the serving beam
quality degrades, without the need for continuous neighbour beam
quality comparisons.
Evaluations indicate also that sudden beam loss is possible due to
shadow fading, e.g., when turning a street corner. The active mode
mobility (AMM) solution includes features that assist in avoiding
or rapidly recovering from a sudden link quality reduction or
out-of-synch condition.
The AMM solution includes both lower-layer procedures (mobility
trigger, measurements, beam selection, RS design, and robustness)
and RRC topics (beam identity management, inter-node handover, and
other higher-layer aspects). The AMM solution supports both beam
switches within one node and between different nodes using
primarily measurements on MRS. Note that the procedures described
in this section can be used to change beams within one node using
measurements on CSI-RS. Or to be more precise: beam-switches using
CSI-RS can be used for cases when the data plane does not have to
be re-routed, and no resynchronization needs to be done. On these
cases, the CSI-RS-based procedure is much leaner, and is also
completely transparent to the UE.
Furthermore, the AMM solution distinguishes between link beams and
mobility beams. Link beams are the beams used for data
transmission, whereas mobility beams are used for mobility
purposes.
The NR system should provide seamless service experience to users
that are moving, and is designed to support seamless mobility with
minimal use of resources. As mentioned above, there is a dormant
mode (referred to above as RRC_CONNECTED DORMANT state) and an
active mode (referred to above as RRC_CONNECTED ACTIVE state) in
NR, which means that the mobility includes the dormant mode
mobility and active mode mobility. The mobility in dormant mode
(location update and paging) is discussed in detail below. In this
section, only the intra-NR active mode mobility is treated. A
description of reference signals used for mobility procedures was
presented above.
There are some specific needs that the mobility solution should
preferably fulfill, which include one or more of: The mobility
solutions shall support movement between beams without any packet
loss. (In LTE, packet forwarding is used--some temporary extra
delay is OK but loss of packets is not.) The mobility solution
shall support multi-connectivity, where coordination features
usable for nodes connected both via excellent backhaul (e.g.,
dedicated fiber) as well as via relaxed backhaul (e.g., latency of
10 ms and above, wired, wireless). The mobility solutions should
work for both analog beamforming and digital beamforming. Mobility
and UE measurements shall work for both synchronized and
unsynchronized access nodes. The mobility solutions shall support
radio link failure detection and recovery actions by the UE. The
mobility solutions shall support movement between NR and all
existing RATs with a tighter integration between NR and LTE with
short inter-RAT handover interruption time.
Desirable design principles for active mode mobility include one or
more of: A mobility framework built of configurable functions shall
be used. Mobility solutions shall have the flexibility that the
downlink and uplink mobility can be triggered and executed
independent to each other. For active mode, mobility solutions
shall be network controlled as a general rule, network configured
UE control can be used to the extent there are proven large gains.
Mobility-related signalling shall follow the ultra-lean principle.
Preferably it shall occur on-demand, to minimize measurement signal
transmission. The signaling overhead and measurement overhead
related to mobility should be minimized. The mobility solutions
shall always maintain a good-enough link between the terminal and
the network (which is different from "always be on the best"). The
mobility solutions should work independently of the "transmission
modes".
Multi-antenna transmission already plays an important role for
current generations of mobile communication and takes on further
importance in NR to provide high data rate coverage. The challenges
facing active mode mobility in NR are related to supporting the
high-gain beam forming. When the link beams are relatively narrow,
the mobility beams should be tracking UEs with high accuracy to
maintain good user experience and avoid link failure.
The downlink mobility concept of NR is beam-based. In deployments
with large antenna arrays and many possible candidate beam
configurations, all beams cannot transmit reference and measurement
signals in an always-on, static manner. Instead, the connected
access nodes select a relevant set of mobility beams to transmit
when required. Each mobility beam carries a unique Mobility
Reference signal (MRS). The UE is then instructed to measure on
each MRS and report to the system. From a UE point of view, this
procedure is independent of on how many access nodes are involved.
As a consequence, the UE does not have to care about which access
node is transmitting which beams; sometimes this is referred to as
the UE being node-agnostic and the mobility being UE-centric. For
mobility to work efficiently, the involved access nodes need to
maintain beam neighbour lists, exchange beam information, and
coordinate MRS usage.
Tracking a moving UE is achieved by the UE measuring and reporting
relevant candidate beams' quality, whereby the system can select
beams for data transmission based on the measurements and
proprietary criteria. The term beam switching is, in this context,
used to describe the event when the access nodes update the
parameters, e.g., transmission point and direction of the beam.
Thus, both intra- and inter-access node beam hand-overs can be seen
as a beam switches. As a consequence, hand-over in NR is executed
between beams rather than cells as in traditional cellular
systems.
The beam type discussed in this section is mainly the mobility
beam, which is the entity to update during mobility. Besides the
mobility beam, there is also a `geo-fence` beam which is introduced
to ease inter-node mobility in some deployments.
The following sections describes downlink mobility: choosing which
beam/node to use for downlink transmission. One section describes
downlink measurement-based mobility and one section describes
uplink measurement-based. So far, it is assumed that the same
beam/node is used for uplink communication. However, in some cases,
it can be advantageous to use different beams/nodes for downlink
and uplink communication. This is called uplink/downlink
decoupling. In that case, a separate procedure may be used to
select the best uplink beam/node. Uplink measurements are used to
select the uplink beam/node, and the procedures described above are
used with minimum changes.
Several detailed studies of mobility solution options have been
carried out, and all these formulations follow a common mobility
framework, which can be summarized at a high level as in FIG. 11,
which illustrates a generic active mode mobility (downlink
measurement based) procedure. After it is decided to trigger a beam
switch, a set of candidate beams are selected for activation and
measurement. These beams may originate both in the serving access
node and in potential target access nodes. Measurements are based
on Mobility Reference Signal (MRS) transmissions in mobility beams.
The network decides the target beam after UE reports the result of
the measurements to the network and optionally informs the UE of
the selected target beam. (Alternatively, the UE may have been
proactively configured to autonomously select the candidate beam
with the best measurement result, and subsequently transmit the
measurement report to the target beam.) The procedure includes one
or more of:
UE side:
Measurement configuration. UE receives the mobility configuration
from network about which MRSs to measure (or the UE could also do a
full blind search without a configured list), when to measure, how
to measure, and how to report. The measurement configuration can be
performed earlier (and continuously updated.) Measurement. UE
performs mobility measurements after UE receives measurement
activation which is instructed to start measuring on some or all of
the entries in the measurement configuration. Measurement report.
UE sends mobility measurement reports to the network Mobility
execution. UE may receive a request to transmit USS in the uplink
for timing advance (TA) measurement and send the USS. The
requirement to send USS can be part of measurement configuration.
UE may receive a command (reconfiguration) to perform beam switch,
which may include a new beam ID and a TA adjust command. The switch
command can also be first informed, and TA can be measured and
adjusted in target node. Or, if the downlink sync and uplink TA
remain valid, and the additional configuration (new DMRS, security,
etc.) is not required or can be informed via target node, the UE
may not receive a switch command. Network side: Measurement
configuration. Network sends mobility measurement configuration to
UE. Mobility trigger. Network determines whether to trigger beam
switching procedure. Mobility measurement. Network decides to
execute mobility measurement procedure which includes: Neighbour
selection: Network selects candidate beams. Measurement
configuration. Network sends measurement configuration to UE if it
is not configured in step 1. Measurement activation. Network
activates MRS in relevant beams and sends a measurement activation
command to UE. Measurement report. Network receives measurement
report from UE. Mobility execution. Network may send a USS request
command (reconfiguration) to UE to transmit USS for TA measurement.
The target node may measure the TA value and send the value to the
node communicating with the UE who will send TA configuration to
the UE. Network may send beam switching (reconfiguration) command
to UE.
Network can send measurement configuration to UE either before
triggering beam switching procedure (step 1) or after (during step
3).
The outlined sequence is configurable with suitable settings to
serve as a common framework for all active mode mobility-related
operations: first-time beam finding, triggered beam mobility update
in data transmission and monitoring modes, and continuous mobility
beam tracking.
A configuration of the generic downlink active mode mobility
procedure where the UE moves from Serving Access Node 1 (SAN1) to
SAN2, as shown in FIG. 11, is described in the following
section
The network may send a mobility measurement configuration to the
UE. This configuration is transmitted in an RRC message and may
contain information related to measurement events--"what" (e.g.,
which MRS indices) to measure, "when" and "how" to measure (e.g.,
start time or criterion and filtering duration), or "when" and
"how" to send a measurement report (e.g., report time slot, report
best beam IDs or also their powers, etc.). The list may be useful
if only a small number of MRS are turned on and can be measured on.
But sending the list can be optional for the Network, NW, and UE
can perform measurements blindly, e.g., detecting all audible MRS
signals. Another example of configurability could be inter-node
measurements where longer filtering may be required to avoid
ping-pong effects. For intra-node beam measurements, a short filter
is used.
A measurement configuration may be sent by the network at any time.
Typically, once the UE receives the configuration, it starts
performing measurements. However, this procedure could be further
enhanced by transmitting an activation command in the downlink
control information (DCI) field. Thus, the RRC message would only
configure the measurement but may not necessary initiate the UE to
start performing such measurements.
The UE sends measurement reports based on the configuration
provided by the network. Measurement reports are typically RRC
messages sent to the network. However, in certain cases, some type
of reports could be sent over MAC. For the Layer 3 based report,
different number of beams can be reported concurrently, allowing to
find the preferred beam in a short time, however it requires more
signaling overhead, and it is not easy to integrate beam switching
with the scheduler. For Layer 2 based reporting, there is less
overhead, and it is easy to integrate with scheduler, however, a
fixed maximum number of beam measurements can be concurrently
reported.
The MRS transmission and measurements are triggered based on the
observed link beam/node quality when data transmission is ongoing,
mobility beam quality in the absence of data, or reports sent by
the UE. Other triggers such as load balancing may also trigger
mobility measurement execution.
There are different trigger metrics and different conditions. The
metric to reflect beam quality is either RSRP or SINR. The
condition can be one or more of: a1) comparison to one absolute
value a2) comparison to multiple different relative values to a
reference table according to position a3) comparison to values of
other beams, or a4) degradation rate of the link beam quality.
Practical trigger mechanisms that react to changes in the current
quality metric have also been demonstrated.
The observed beam can be one or more of the: b1) current serving
link beam (DMRS or CSI-RS), b2) current serving link beam plus its
`sector` beam, b3) current serving mobility beam (MRS).
The different types of switching (e.g., intra-node or inter-node)
may have different thresholds. For example, when link quality is
worse than threshold 1, intra-node beam switch is triggered. When
link quality is worse than threshold 2, inter-node beam evaluation
and switching is triggered. If excellent backhaul (e.g., dedicated
fiber) is present and there is no problem with ping-pong effects,
both intra-node and inter-node can use the same parameters.
When the network decides that a serving beam/node identity need to
be changed/updated/modified, the network prepares the mobility
procedure. This may imply some communication with other nodes in
the network.
There are several options for reporting the MRS measurement results
to the network: c1) If the UE reports all measurements to the
serving node, the serving node determines the node to switch to and
signals to the UE. This approach relies on the existing serving
link for all signaling during the mobility procedure. TA towards
the new serving beam is estimated in conjunction with the switch
command. c2) If the UE reports the measurements back to the
individual nodes where the different MRS came from, the reporting
itself requires a previous USS transmission and TA estimation--it
is then seen as part of the measurement procedure. Once the Network
has decided the new serving node and signaled to the UE, the UE
uses the already available TA towards the new serving node. This
approach requires more uplink signaling, but removes the critical
dependence on the old serving link once the measurement command has
been issued. c3) Similar to c2), but the UE reports all the
measurements back via the serving beam and via the best of the
measured new beams. Then, only one TA estimation procedure should
be conducted.
Eventually, the network may request the UE to apply a new
configuration. There may be situations in which a reconfiguration
could be transparent for the UE, e.g., in an intra-node beam
switch. The reconfiguration then happens on the network side, a
serving beam/node may be changed; however, the UE keeps the
existing configuration. If a reconfiguration is needed, it can be
configured before or after the switch.
In general, the MRS is only transmitted based on demand. The
network decides which candidate beams, or neighbour beams, should
be activated. Candidate beam selection can be based on, e.g., a
beam relations lookup table. This neighbourhood lookup table is
indexed by either UE position or radio fingerprint. The position
can be the accurate position (e.g., Global Positioning System (GPS)
info) or an approximate position (current serving beam info).
Creating and maintaining the neighbourhood lookup tables is a
generalization of the automatic neighbour relations (ANR)
management process, handled by the SON functionality in the
network. The tables can be used both for providing trigger criteria
to initiate a measurement session towards a given UE and for
determining the relevant candidate beams for measurements and a
possible beam switch. The beam in this lookup table can be either a
normal mobility beam or a `sector` beam. The neighbour beam
relationship table size can be reduced; both from the memory
consumption and from the signaling consumption perspective, if the
candidate beams are wide and the number of beams is lower. In some
network deployments, e.g., deploying NR in LTE frequency bands or
in a high load and frequent handover area, it may be preferable to
configure the MRS to be always-on, so that potentially many UEs
that are covered by the same mobility beams can continuously track
the quality of neighbour beams.
To report MRS measurements to nodes other than the serving node,
and to resume uplink data transmission towards a new serving node,
the UE needs to apply correct timing advance, which typically
differs from the TA for the current serving node. In a non-synched
Network, the TA estimation always needs to be performed. USS
transmission is then configured per-measurement in the MRS
measurement command or statically by RRC. The same applies in
synched macro NWs, where the ISD, Inter Site Distance, exceeds or
is comparable to the CP length.
In a tightly synched Network with short ISDs (Inter Site
Distances), on the other hand, the TA towards the old serving node
may also work well for a new serving node. The UE can deduce
whether that is the case from whether the old downlink timing sync
works for the new node. It would be efficient not to do new TA
estimation unless really necessary. The network-controlled approach
is that the network configures the UE to transmit the USS (or not)
on a per-measurement basis in the MRS measurement command. TA is
not estimated if the network estimates that the old and new nodes
can share the same TA value, otherwise the UE is requested to send
USS. Alternatively, in a UE-controlled approach, the UE can omit
sending USS in the uplink if it determines that no re-sync was
necessary to measure the new node's MRS. Here, the node still needs
to reserve resources for USS reception.
If the TA is to be changed, this is conveyed using dPDCH or PCCH
either over the old serving beam or from the new node (where the
downlink is already "operational" since the UE has synched to the
MRS).
In MRS reporting solution c1 above, the USS may be sent in the
uplink and TA update in the downlink may be sent as part of the
beam switch command and handshake.
In MRS reporting solutions c2 and c3 above, the UE sends the USS as
part of the measurement report procedure towards an
MRS-transmitting node, and receives a TA update as a separate
message.
In some deployments, where the UE position may be determined with
high accuracy, the required TA correction when switching from old
serving beam to a new one may be retrieved from a previously
collected database. The database is created based on previous TA
measurements managed according to SON principles.
The mobility measurement sequences are essentially the same as in
LTE. The mobility monitoring and triggering sequences are similar
to those in LTE, but some details differ, e.g., the criteria of
launching and the UE-specific signals available for mobility
measurements. The MRS activation sequence where reference signals
(MRS) are activated dynamically in a UE-specific candidate beam set
is a new procedure in NR. Activating and deactivating MRS on
request, and in a UE specific manner is critical for lean design.
The main new challenge in NR is for the network to decide which
candidate MRSs are activated, and when. The latter aspect may be
especially critical at high frequencies due to shadow fading. Some
preparations and signaling may be needed in the network when
candidate beams are activated in several different nodes.
Nevertheless, this procedure is transparent to the UE. The UE is
only informed about the measurement configuration and the UE
reports accordingly, without having associated the beams with
specific nodes. The TA update sequences can also be measured and
adjusted in target node after the switch command is first informed.
Also, the additional reconfiguration is probably required.
The beam switch triggering procedure differs depending on how MRS
is designed and transmitted. More specifically there are three
typical cases: The beam MRS is only activated when serving beam
quality degradation is detected. MRS for all relevant candidate
beams in the lookup table are activated, no matter if the beam is
from the same node or from a neighbouring node. The table building
can be part of the SON functions. The UE measures on all the MRSs
and sends the measurement report. Either all the sector MRSs in the
lookup table or the sector MRS containing the serving beam for the
active UE is configured and transmitted periodically. UE can also
keep track of the quality of the transmitted sector MRS and report
the quality periodically or in an event-based manner. The serving
mobility beam is adapted to continuously track the UE to maintain
the maximum beam gain, which is similar to the CSI-RS procedures.
The UE reports an error signal between the current serving beam
direction and the estimated best beam direction, using additional
beams in the neighbourhood of the serving beam.
Case 1 is more suitable for services without strict QoS
requirements, while case 2 is more suitable for time critical
service with additional overhead. (There are also hybrid options,
e.g., activating all the MRSs in the lookup table for a given UE,
with additional overhead.) In case 3, with UE specific reference
symbols, any modification of beam shape within one node can be
transparent to the UE--no signaling is required, unless RX analog
beamforming is applied in the UE side.
It is also possible to use uplink measurements to select downlink
beam. On a high level, it can be assumed that such measurements are
performed on demand, when a beam switch is deemed necessary. Hence,
the concept of a mobility event still applies, and some sort of
trigger to start the event is relied upon.
Since the downlink beam is being updated, it is natural to still
monitor the downlink performance, using any of the measurements
described in the previous section. For instance, CQI measured on
CSI-RS or MRS may be monitored.
Using uplink measurements to choose the access node used for
downlink transmission usually works well, providing that different
access nodes use the same transmit power and have the same antenna
capabilities. Otherwise, this has to be compensated for.
To use uplink measurements to select downlink beam within one node,
reciprocity between uplink and downlink is desirable. Passive
antenna components and the propagation medium are physically
reciprocal for TX and RX, but active components and radio-frequency
(RF) filters in the RX and TX paths typically exhibit asymmetries
and phase variations that do not yield automatic reciprocity in all
cases. However, by introducing additional hardware design
constraints and calibration procedures, any desirable degree of
reciprocity may be provided.
To obtain the uplink measurement, the network requests the UE to
send uplink reference signals to the network. One possible
reference signal for mobility measurements is the USS. The USS can
be detected not only by the serving node, but also by the neighbour
nodes. The neighbour nodes should hold transmissions of UEs that
they are serving, to clear the transmission resources where the USS
will occur.
If the coverage situation is challenging, the UEs may need to use
TX beamforming to transmit the USS. In this case, the UE is
required to transmit the USS in all candidate directions, and
different USS identities may be allocated to different uplink TX
beams in the UE side so that the network can feed back the best UE
TX beam identities. If the UE cannot transmit in more than one
direction simultaneously, the beams transmissions may be
time-multiplexed. The USS can be transmitted from the UE
periodically or be event triggered (when the quality of the link
beams degrades). Such beam sweep configuration is more complicated
in the uplink than in the downlink, due to the irregular UE antenna
array layout. Suitable sweep patterns may be determined in several
ways using prior calibration or on-the-fly learning by the UE.
In the network, the candidate access node attempts to detect the
USS in different beams, and selects the best beam. If analog beam
forming is used by the network, the nodes cannot perform the
measurement of a large number of beams in one USS period. The
access node can scan the USS using different RX beams sequentially.
Coordination of UE TX and access node RX beam sweep patterns is
complicated. Relying on this combination should only be considered
if really mandated by the coverage requirements.
There are some requirements on signaling between UE and network,
which include, e.g., the number of USS used in UE and the
repetition period for network scanning. It may be assumed that the
same procedure is adopted as for MRS configuration: configure USS
transmission parameters using RRC, and activate transmission using
MAC.
There are several alternatives to perform downlink beam switching
based on the uplink measurement: The narrow (link) beam can be
selected directly based on the uplink measurement. The beam
selection based on the uplink measurement decides the mobility
beam, and the narrow (link) beam can be selected based on the
complemented downlink measurement later. The mobility beam is first
decided by the uplink measurement with a wider RX beam. After that,
the narrow (link) beam can be further decided by uplink
measurements with narrow RX beam. When deciding the narrow beam,
the other RS might be measured in the narrow beams that are located
within, or in the vicinity of, the selected RX beams in first
part.
In the three beam-switching alternatives listed immediately above,
the beam-selection procedures (beam selection in the first
alternative; wide beam selection in the second and third
alternatives) are similar/ An example beam-selection procedure is
illustrated in FIG. 12. The procedure of the beam selection based
on the uplink measurement can briefly be expressed as follows:
Trigger beam switch Activate USS reception between neighbour nodes
in relevant beams Activate USS transmission in UE Perform USS
measurement in network Determine the best beam based on the
measurement report Prepare beam switch if needed Issue beam switch
command if needed
As said previously, the USS can be transmitted from the UE
periodically, or in an event-triggered manner. If the USS is
transmitted periodically according to the early configuration,
steps 1-3 can be ignored. If a timing advance update is needed, the
TA value can be obtained from the USS measurement and the new TA
value can be informed to UE during beam switch command.
For the narrow (link) beam selection that follows the mobility beam
selection in the third downlink beam-switching alternative listed
above, there is only one small difference, where the beams from
neighbour node are not involved. It is a kind of intra-node beam
selection, which is illustrated in FIG. 13. Here the "USS" could
also be other type of reference, such as RRS. The complemented
downlink measurement in the second alternative above is similar to
the intra-Node beam switch in case 2 of downlink measurement based
method.
Described in this section are several additional techniques that
complement the techniques descried above. In various embodiments,
any one or more of these additional techniques may be implemented
along with any combination of the techniques described above.
In NR, the amount of CSI generally increases with the number of
antennas/beams, meaning that the number of evaluations of
beams/hypothesis performed by the UE can increase accordingly. This
will in turn lead to an increase in UE power consumption.
One approach to address this, and to thus lower UE power
consumption, is to have at least two reporting modes for CSI. One
mode is a mode where the UE or other wireless device seeks the
"best" transmission configuration. This may be regarded as a
"default" or "legacy" mode. Another mode may be referred to as a
"low-power mode," and is based on the use of a threshold for the
quality of the reported CSI (e.g., PMI). In this mode, the UE
reports (to the wireless network) the first CSI/PMI that meets a
quality threshold requirement. Thus, rather than finding the
absolute best possible transmission configuration, the UE instead
finds one that is sufficient to meet the quality threshold
requirement, and reports it, reducing UE power consumption by not
necessarily seeking the absolute best possible transmission
configuration. In certain embodiments, the UE may select the
threshold for the quality of the reported CSI by itself, based on
pre-programmed quality thresholds or other selection criteria. In
alternative embodiments, the UE may receive a direction from the
network as to the threshold for the quality of the reported CSI,
and select the directed threshold.
In some embodiments, this low power mode may involve the UE only
scanning a subset of the PMI, for example. This low power mode may
also involve the UE turning off one or more receiver/transmitter
chains or, more generally, switching one or more receiver and/or
transmitter circuits to a low-power state while operating in the
low power mode, such that the circuits consume less power in this
low-power state relative to their power consumption in the default
mode. This low-power mode allows the evaluations of beams to be
discontinued once a sufficiently good beam is found, saving power
consumption. An advantage of this approach is that for most
signaling of small packets, the UEs can use a CSI reporting mode
that saves a significant amount of energy.
In NR, a UE operating in dormant mode (e.g., RRC_CONNECTED DORMANT
state) searches for synchronization signals and other system
information, as was described in detail in sections above. In a
system where beamforming is in use, the UE searches for these
synchronization signals and other system information across an
interval of possible resources, where that interval covers various
combinations of time, frequency, and spatial beam. Note that this
freedom with respect to resources does not exist in LTE.
A potential problem with this is that a dormant UE may need to stay
awake for much longer periods to perform this searching, as
compared to when operating in LTE. This can have a negative impact
on power consumption by the UE.
This problem may be addressed, in some embodiments, by having the
UE go (back) to sleep as soon as it has received sufficiently good
system information and/or synchronization, where "sufficiently
good" is determined by meeting a predetermined threshold or
thresholds, without necessarily searching over an entire
predetermined search interval. This approach allows the UE to
realize power savings, especially in environments with good
signals.
FIG. 14 is a process flow diagram illustrating an example method
according to this approach. As shown at block 1410, the method
begins with performing a measurement and/or demodulating/decoding,
for synchronization and/or system information, on one of a
predetermined set of resources, where the resources are defined by
one or more of beam, timing, and frequency. As shown at block 1420,
the method further includes determining whether sufficient
synchronization and/or system information has been obtained, as a
result of the measurement and/or demodulating/decoding on the
current resource. If so, the method further includes, as shown at
block 1430, performing one or more actions based on the
measurement, if and to the extent that such an action is required,
and going back to "sleep," where "sleep" refers to a lower-power
mode of operation for the UE's circuitry, as compared to the
operating mode in which the measurements are actively performed.
If, on the other hand, it is determined that sufficient
synchronization and/or information is not obtained, a next resource
from the predetermined set of resources is assigned, as shown at
block 1440, and the measuring and/or demodulating/decoding step
shown in block 1410 is repeated.
An advantage of this technique is that UE power consumption in
dormant mode may be reduced, in some cases to lower levels than
achieved in conventional LTE operation. Note that "dormant mode" as
used herein refers generally to a mode where a wireless device
intermittently activates receiver circuitry to monitor and/or
measure signals, deactivating at least parts of the receiver
circuitry in between these monitoring/measuring intervals. These
periods where some of the circuitry is deactivated may be referred
to as "sleep" periods. In the discussion above, NR is described as
having a dormant mode referred to as RRC_CONNECTED DORMANT state.
However, it will be appreciated that there may be one or several
dormant modes supported by any given network, with names that
vary.
FIG. 15 illustrates another example process, involving a UE dormant
mode measurement procedure where beamformed cell information
signals are received and processed according. Below, the steps in
the figure are explained in detail.
As shown at block 1510, a UE in dormant mode triggers a measurement
occasion based on any of various triggers. For a typical cellular
system, this may be periodic with a period on the order of 1
second.
As shown at block 1520, the UE forms a list of cell information
signals and corresponding radio resources, where this list
represents those signals and resources it is already aware of, or
which it knows may be present. The radio resources can be beams,
time intervals, and other radio resource groups (such as OFDM
resource elements, for example) where the cell information signals
may be present.
As shown at block 1530, the UE sorts the resource and signal list
in an order based on for example (but not limited to): Radio
resource timing (first signals first etc.) Known signal quality or
measurement property from previous measurement occasions
Information of likelihood of usefulness from other sources, cell
neighbour lists, other measurements, etc.
The sort order is so that the highest prioritized cell information
signal (or resource) is first in the list.
As shown at block 1540, the UE uses its radio receiver to receive
radio resources for the first item(s) in the list. While receiving
this, the measurement signal processing of previously collected
resource may still be ongoing.
As shown at block 1550, the UE measures the desured signal
properties from the collected radio resources. These may include
(but are not limited to) any one or more of: Received signal power
Received signal SINR or SNR Decodability of cell information
Decoded information such as paging information from the cellular
network.
As shown at block 1560, the UE decides, based on one or more of the
measured signal properties from 1550, whether the measurements
collected so far are "good enough" to stop measuring and cell
search activities. If not, the measurements continue, as shown at
block 1540. "Good enough" generally refers to the satisfaction of
one or more predetermined criterion, which may include one or more
of: The received power, SINR or SNR being above a certain threshold
That cell information can be properly decoded That something in the
cell information indicates that a change in mode is needed (for
example a paging indication).
"Good enough" can furthermore be that a given number, e.g. 3, of
the measured cells are detected to be "Good cells".
As shown at block 1570, determining that the measured signals are
"good enough" leads to an end of the measurement occasion. The UE
then reverts to its normal procedures, which may include reporting
measurements, deactivating one or more receiver circuits, etc.
A key aspect of the solution illustrated in FIG. 15 is that a UE in
a cellular system with beamformed cell information, and in dormant
mode, collects measurements for each measurement occasion only up
until a point where the collected information is "good enough".
This allows the UE to save power by going back to sleep before
doing an exhaustive search for all possible cell information
signals.
FIG. 16 shows another example method, implemented by a UE or other
wireless device, for operating in a wireless communications
network. This method is similar, at least in some respects, to the
previously illustrated methods--it will be appreciated that
features of this method may be mixed and matched, as appropriate
with features of the methods described above.
The method 1600 shown in FIG. 16 is carried out while the UE is
operating in a dormant mode, wherein operating in the dormant mode
comprises intermittently activating receiver circuitry to monitor
and/or measure signals. This dormant mode may be, for example, the
RRC_CONNECTED DORMANT state discussed earlier. The UE carries out
the steps shown in FIG. 16 while in this dormant mode, and while
the receiver circuitry is activated.
As shown at block 1610, the UE performs a measurement on each of a
plurality of resources from a predetermined set of resources, or
demodulates and decodes information from each of a plurality of
resources from a predetermined set of resources, where the
resources in the predetermined set of resources are each defined by
one or more of a beam, a timing, and a frequency. In some
embodiments, the resources in this predetermined set of resources
are each defined as a beam. Each of these may represent a receiver
beam (where the UE is "listening" in different directions using a
particular combination of antennas and combining weights) or a
particular transmitter beam as formed by an access node, or a
combination of both.
As shown at block 1620, the method further includes evaluating the
measurement or the demodulated and decoded information for each of
the plurality of resources against a predetermined criterion. As
shown at block 1630, the UE then discontinues the performing and
evaluating of measurements, or discontinues the demodulating and
decoding and evaluation of information, in response to determining
that the predetermined criterion is met, such that one or more
resources in the predetermined set of resources are neither
measured nor demodulated and decoded. Finally, as shown at block
1640, the method further comprises deactivating the activated
receiver circuitry, further in response to determining that the
predetermined criterion is met. The steps in the figure may be
repeated at the next occurrence of a triggering event that
re-activates the receiver circuitry, in some embodiments, for
example upon the periodic expiration of a dormant mode timer.
In some embodiments, the predetermined criterion comprises one or
more of the following: that a received power level, or a measured
signal-to-interference-plus-noise ratio (SINR), or a
signal-to-noise ratio (SNR) is above a predetermined threshold, for
one or for a predetermined number of resources; that cell
information can be correctly decoded from one or for a
predetermined number of resources; and that decoded information
from one or for a predetermined number of resources instructs a
change in operation for the wireless device.
In some embodiments, the discontinuing is performed in response to
determining that the predetermined criterion is met for one of the
resources. In some embodiments, the method further comprises, prior
to said performing or demodulating and decoding, and prior to said
evaluating, discontinuing, and deactivating, determining a priority
order for the predetermined set of resources, from highest to
lowest, wherein said performing or demodulating and decoding is
according to the priority order, from highest to lowest. This
determining the priority order for the predetermined set of
resources may be based on one or more of any of the following, for
example: radio resource timing for one or more of the resources;
and measured signal qualities or measurement properties from
previous measurements of one or more of the resources. In some
embodiments, determining the priority order for the predetermined
set of resources is based on information regarding likelihood of
usefulness for one or more of the resources, the information being
received from other sources or cell neighbour lists.
In this section, some of the many detailed techniques and
procedures described above are generalized and applied to specific
methods, network nodes, and wireless devices. Each of these
methods, radio network equipment, and wireless devices, as well as
the numerous variants of them that are described in the more
detailed description above, may be regarded as an embodiment of the
present invention. It should be understood that the particular
groupings of these features described below are examples--other
groupings and combinations are possible, as evidenced by the
preceding detailed discussion.
Note that in the discussion that follows and in the claims appended
hereto, the use of labels "first," "second," "third," etc., is
meant simply to distinguish one item from another, and should not
be understood to indicate a particular order or priority, unless
the context clearly indicates otherwise.
As used herein, "wireless device" refers to a device capable,
configured, arranged and/or operable to communicate wirelessly with
network equipment and/or another wireless device. In the present
context, communicating wirelessly involves transmitting and/or
receiving wireless signals using electromagnetic signals. In
particular embodiments, wireless devices may be configured to
transmit and/or receive information without direct human
interaction. For instance, a wireless device may be designed to
transmit information to a network on a predetermined schedule, when
triggered by an internal or external event, or in response to
requests from the network. Generally, a wireless device may
represent any device capable of, configured for, arranged for,
and/or operable for wireless communication, for example radio
communication devices. Examples of wireless devices include, but
are not limited to, user equipment (UE) such as smart phones.
Further examples include wireless cameras, wireless-enabled tablet
computers, laptop-embedded equipment (LEE), laptop-mounted
equipment (LME), USB dongles, and/or wireless customer-premises
equipment (CPE).
As one specific example, a wireless device may represent a UE
configured for communication in accordance with one or more
communication standards promulgated by the 3rd Generation
Partnership Project (3GPP), such as 3GPP's GSM, UMTS, LTE, and/or
5G standards. As used herein, a "user equipment" or "UE" may not
necessarily have a "user" in the sense of a human user who owns
and/or operates the relevant device. Instead, a UE may represent a
device that is intended for sale to, or operation by, a human user
but that may not initially be associated with a specific human
user. It should also be appreciated that in the previous detailed
discussion, the term "UE" is used, for convenience, even more
generally, so as to include, in the context of the NR network, any
type of wireless device that accesses and/or is served by the NR
network, whether or not the UE is associated with a "user" per se.
Thus, the term "UE" as used in the above detailed discussion
includes machine-type-communication (MTC) devices (sometimes
referred to as machine-to-machine, or M2M devices), for example, as
well as handsets or wireless devices that may be associated with a
"user."
Some wireless devices may support device-to-device (D2D)
communication, for example by implementing a 3GPP standard for
sidelink communication, and may in this case be referred to as D2D
communication devices.
As yet another specific example, in an Internet of Things (IOT)
scenario, a wireless device may represent a machine or other device
that performs monitoring and/or measurements, and transmits the
results of such monitoring and/or measurements to another wireless
device and/or a network equipment. A wireless device may in this
case be a machine-to-machine (M2M) device, which may in a 3GPP
context be referred to as a machine-type communication (MTC)
device. As one particular example, a wireless device may be a UE
implementing the 3GPP narrow band internet of things (NB-IoT)
standard. Particular examples of such machines or devices are
sensors, metering devices such as power meters, industrial
machinery, or home or personal appliances, e.g. refrigerators,
televisions, personal wearables such as watches etc. In other
scenarios, a wireless device may represent a vehicle or other
equipment that is capable of monitoring and/or reporting on its
operational status or other functions associated with its
operation.
A wireless device as described above may represent the endpoint of
a wireless connection, in which case the device may be referred to
as a wireless terminal. Furthermore, a wireless device as described
above may be mobile, in which case it may also be referred to as a
mobile device or a mobile terminal.
Although it will be appreciated that specific embodiments of the
wireless devices discussed herein may include any of various
suitable combinations of hardware and/or software, a wireless
device configured to operate in the wireless communications
networks described herein and/or according to the various
techniques described herein may, in particular embodiments, be
represented by the example wireless device 1000 shown in FIG.
17.
As shown in FIG. 17, example wireless device 1000 includes an
antenna 1005, radio front-end circuitry 1010, and processing
circuitry 1020, which in the illustrated example includes a
computer-readable storage medium 1025, e.g., one or more memory
devices. Antenna 1005 may include one or more antennas or antenna
arrays, and is configured to send and/or receive wireless signals,
and is connected to radio front-end circuitry 1010. In certain
alternative embodiments, wireless device 1000 may not include
antenna 1005, and antenna 1005 may instead be separate from
wireless device 1000 and be connectable to wireless device 1000
through an interface or port.
Radio front-end circuitry 1010, which may comprise various filters
and amplifiers, for example, is connected to antenna 1005 and
processing circuitry 1020 and is configured to condition signals
communicated between antenna 1005 and processing circuitry 1020. In
certain alternative embodiments, wireless device 1000 may not
include radio front-end circuitry 1010, and processing circuitry
1020 may instead be connected to antenna 1005 without radio
front-end circuitry 1010. In some embodiments, radio-frequency
circuitry 1010 is configured to handle signals in multiple
frequency bands, in some cases simultaneously.
Processing circuitry 1020 may include one or more of
radio-frequency (RF) transceiver circuitry 1021, baseband
processing circuitry 1022, and application processing circuitry
1023. In some embodiments, the RF transceiver circuitry 1021,
baseband processing circuitry 1022, and application processing
circuitry 1023 may be on separate chipsets. In alternative
embodiments, part or all of the baseband processing circuitry 1022
and application processing circuitry 1023 may be combined into one
chipset, and the RF transceiver circuitry 1021 may be on a separate
chipset. In still alternative embodiments, part or all of the RF
transceiver circuitry 1021 and baseband processing circuitry 1022
may be on the same chipset, and the application processing
circuitry 1023 may be on a separate chipset. In yet other
alternative embodiments, part or all of the RF transceiver
circuitry 1021, baseband processing circuitry 1022, and application
processing circuitry 1023 may be combined in the same chipset.
Processing circuitry 1020 may include, for example, one or more
central processing units (CPUs), one or more microprocessors, one
or more application-specific integrated circuits (ASICs), and/or
one or more field programmable gate arrays (FPGAs).
In particular embodiments, some or all of the functionality
described herein as relevant to a user equipment, MTC device, or
other wireless device may be embodied in a wireless device or, as
an alternative, may be embodied by the processing circuitry 1020
executing instructions stored on a computer-readable storage medium
1025, as shown in FIG. 17. In alternative embodiments, some or all
of the functionality may be provided by the processing circuitry
1020 without executing instructions stored on a computer-readable
medium, such as in a hard-wired manner. In any of those particular
embodiments, whether executing instructions stored on a
computer-readable storage medium or not, the processing circuitry
1020 can be said to be configured to perform the described
functionality. The benefits provided by such functionality are not
limited to the processing circuitry 1020 alone or to other
components of the wireless device, but are enjoyed by the wireless
device as a whole, and/or by end users and the wireless network
generally.
The processing circuitry 1020 may be configured to perform any
determining operations described herein. Determining as performed
by processing circuitry 1020 may include processing information
obtained by the processing circuitry 1020 by, for example,
converting the obtained information into other information,
comparing the obtained information or converted information to
information stored in the wireless device, and/or performing one or
more operations based on the obtained information or converted
information, and as a result of said processing making a
determination.
Antenna 1005, radio front-end circuitry 1010, and/or processing
circuitry 1020 may be configured to perform any transmitting
operations described herein. Any information, data and/or signals
may be transmitted to a network equipment and/or another wireless
device. Likewise, antenna 1005, radio front-end circuitry 1010,
and/or processing circuitry 1020 may be configured to perform any
receiving operations described herein as being performed by a
wireless device. Any information, data and/or signals may be
received from a network equipment and/or another wireless
device
Computer-readable storage medium 1025 is generally operable to
store instructions, such as a computer program, software, an
application including one or more of logic, rules, code, tables,
etc. and/or other instructions capable of being executed by a
processor. Examples of computer-readable storage medium 1025
include computer memory (for example, Random Access Memory (RAM) or
Read Only Memory (ROM)), mass storage media (for example, a hard
disk), removable storage media (for example, a Compact Disk (CD) or
a Digital Video Disk (DVD)), and/or any other volatile or
non-volatile, non-transitory computer-readable and/or
computer-executable memory devices that store information, data,
and/or instructions that may be used by processing circuitry 1020.
In some embodiments, processing circuitry 1020 and
computer-readable storage medium 1025 may be considered to be
integrated.
Alternative embodiments of the wireless device 1000 may include
additional components beyond those shown in FIG. 17 that may be
responsible for providing certain aspects of the wireless device's
functionality, including any of the functionality described herein
and/or any functionality necessary to support the solution
described above. As just one example, wireless device 1000 may
include input interfaces, devices and circuits, and output
interfaces, devices and circuits. Input interfaces, devices, and
circuits are configured to allow input of information into wireless
device 1000, and are connected to processing circuitry 1020 to
allow processing circuitry 1020 to process the input information.
For example, input interfaces, devices, and circuits may include a
microphone, a proximity or other sensor, keys/buttons, a touch
display, one or more cameras, a USB port, or other input elements.
Output interfaces, devices, and circuits are configured to allow
output of information from wireless device 1000, and are connected
to processing circuitry 1020 to allow processing circuitry 1020 to
output information from wireless device 1000. For example, output
interfaces, devices, or circuits may include a speaker, a display,
vibrating circuitry, a USB port, a headphone interface, or other
output elements. Using one or more input and output interfaces,
devices, and circuits, wireless device 1000 may communicate with
end users and/or the wireless network, and allow them to benefit
from the functionality described herein.
As another example, wireless device 1000 may include power supply
circuitry 1030. The power supply circuitry 1030 may comprise power
management circuitry. The power supply circuitry may receive power
from a power source, which may either be comprised in, or be
external to, power supply circuitry 1030. For example, wireless
device 1000 may comprise a power source in the form of a battery or
battery pack which is connected to, or integrated in, power supply
circuitry 1030. Other types of power sources, such as photovoltaic
devices, may also be used.
As a further example, wireless device 1000 may be connectable to an
external power source (such as an electricity outlet) via an input
circuitry or interface such as an electrical cable, whereby the
external power source supplies power to power supply circuitry
1030.
Power supply circuitry 1030 may be connected to radio front-end
circuitry 1010, processing circuitry 1020, and/or computer-readable
storage medium 1025 and be configured to supply wireless device
1000, including processing circuitry 1020, with power for
performing the functionality described herein.
Wireless device 1000 may also include multiple sets of processing
circuitry 1020, computer-readable storage medium 1025, radio
circuitry 1010, and/or antenna 1005 for different wireless
technologies integrated into wireless device 1000, such as, for
example, GSM, WCDMA, LTE, NR, WiFi, or Bluetooth wireless
technologies. These wireless technologies may be integrated into
the same or different chipsets and other components within wireless
device 1000.
Wireless device 1000, in various embodiments, is adapted to carry
out any of a variety of combinations of the features and techniques
described herein. In some embodiments, for example, processing
circuitry 1020, e.g., using antenna 1005 and radio front-end
circuitry 1010, is adapted to, while operating in dormant mode, and
while receiver circuitry is activated, perform a measurement on
each of a plurality of resources from a predetermined set of
resources or demodulating and decoding information from each of a
plurality of resources from a predetermined set of resources, where
the resources in the predetermined set of resources are each
defined by one or more of a beam, a timing, and a frequency. The
processing circuitry 1020 may be further adapted to evaluate the
measurement or the demodulated and decoded information for each of
the plurality of resources against a predetermined criterion, and
to then discontinue the performing and evaluating of measurements,
or discontinue the demodulating and decoding and evaluation of
information, in response to determining that the predetermined
criterion is met, such that one or more resources in the
predetermined set of resources are neither measured nor demodulated
and decoded. The processing circuitry 1020 may be further adapted
to deactivate the activated receiver circuitry, further in response
to determining that the predetermined criterion is met.
Once again, the wireless devices adapted to operate in a dormant
mode according to any of the several techniques described above may
be further adapted to carry out one or more of the several other
techniques described herein. Thus, for example, the resources in
the predetermined set of resources may each be defined as a beam,
in some embodiments, and in various embodiments the predetermined
criterion may comprise one or more of the following: that a
received power level, or a measured
signal-to-interference-plus-noise ratio (SINR), or a
signal-to-noise ratio (SNR) is above a predetermined threshold, for
one or for a predetermined number of resources; that cell
information can be correctly decoded from one or for a
predetermined number of resources; that decoded information from
one or for a predetermined number of resources instructs a change
in operation for the wireless device.
In some embodiments, the wireless device is adapted to carry out
said discontinuing in response to determining that the
predetermined criterion is met for one of the resources. In some of
these and in some other embodiments, the wireless device is further
adapted to, prior to said performing or demodulating and decoding,
and prior to said evaluating, discontinuing, and deactivating,
determine a priority order for the predetermined set of resources,
from highest to lowest, wherein the wireless device is adapted to
carry out said performing or demodulating and decoding is according
to the priority order, from highest to lowest. In some of these
latter embodiments, the wireless device is adapted to determine the
priority order for the predetermined set of resources based on one
or more of: radio resource timing for one or more of the resources;
and measured signal qualities or measurement properties from
previous measurements of one or more of the resources. In some of
these and in some other embodiments, the wireless device is adapted
to determine the priority order for the predetermined set of
resources based on information regarding likelihood of usefulness
for one or more of the resources, said information being received
from other sources or cell neighbour lists.
As used herein, the term "network equipment" refers to equipment
capable, configured, arranged and/or operable to communicate
directly or indirectly with a wireless device and/or with other
equipment in the wireless communication network that enable and/or
provide wireless access to the wireless device. Examples of network
equipment include, but are not limited to, access points (APs), in
particular radio access points. Network equipment may represent
base stations (BSs), such as radio base stations. Particular
examples of radio base stations include Node Bs, and evolved Node
Bs (eNBs). Base stations may be categorized based on the amount of
coverage they provide (or, stated differently, their transmit power
levels) and may then also be referred to as femto base stations,
pico base stations, micro base stations, or macro base stations.
"Network equipment" also includes one or more (or all) parts of a
distributed radio base station such as centralized digital units
and/or remote radio units (RRUs), sometimes referred to as Remote
Radio Heads (RRHs). Such remote radio units may or may not be
integrated with an antenna as an antenna integrated radio. Parts of
a distributed radio base stations may also be referred to as nodes
in a distributed antenna system (DAS).
As a particular non-limiting example, a base station may be a relay
node or a relay donor node controlling a relay.
Yet further examples of network equipment include multi-standard
radio (MSR) radio equipment such as MSR BSs, network controllers
such as radio network controllers (RNCs) or base station
controllers (BSCs), base transceiver stations (BTSs), transmission
points, transmission nodes, Multi-cell/multicast Coordination
Entities (MCEs), core network nodes (e.g., Mobility Switching
Centers or MSCs, Mobility Management Entities or MMEs), Operation
and Maintenance (O&M) nodes, Operation and Support System (OSS)
nodes, SON nodes, positioning nodes (e.g., E-SMLCs), and/or MDTs.
More generally, however, network equipment may represent any
suitable device (or group of devices) capable, configured,
arranged, and/or operable to enable and/or provide a wireless
device access to the wireless communication network or to provide
some service to a wireless device that has accessed the wireless
communication network.
As used herein, the term "radio network equipment" is used to refer
to network equipment that includes radio capabilities. Thus,
examples of radio network nodes are the radio base stations and
radio access points discussed above. It will be appreciated that
some radio network equipment may comprise equipment that is
distributed--such as the distributed radio base stations (with RRHs
and/or RRUs) discussed above. It will be appreciated that the
various references herein to eNBs, eNodeBs, Node Bs, and the like
are referring to examples of radio network equipment. It should
also be understood that the term "radio network equipment" as used
herein may refer to a single base station or a single radio node,
in some cases, or to multiple base stations or nodes, e.g., at
different locations. In some cases, this document may refer to an
"instance" of radio network equipment, to more clearly describe
certain scenarios where multiple distinct embodiments or
installations of radio equipment are involved. However, the lack of
reference to an "instance" in connection with a discussion of radio
network equipment should not be understood to mean that only a
single instance is being referred to. A given instance of radio
network equipment may alternatively be referred to as a "radio
network node," where the use of the word "node" denotes that the
equipment referred to operate as a logical node in a network, but
does not imply that all components are necessarily co-located.
While radio network equipment may include any suitable combination
of hardware and/or software, an example of an instance of radio
network equipment 1100 is illustrated in greater detail by FIG. 18.
As shown in FIG. 18, example radio network equipment 1100 includes
an antenna 1105, radio front-end circuitry 1110, and processing
circuitry 1120, which in the illustrated example includes a
computer-readable storage medium 1025, e.g., one or more memory
devices. Antenna 1105 may include one or more antennas or antenna
arrays, and is configured to send and/or receive wireless signals,
and is connected to radio front-end circuitry 1110. In certain
alternative embodiments, radio network equipment 1100 may not
include antenna 1005, and antenna 1005 may instead be separate from
radio network equipment 1100 and be connectable to radio network
equipment 1100 through an interface or port. In some embodiments,
all or parts of radio front-end circuitry 1110 may be located at
one or several locations apart from the processing circuitry 1120,
e.g., in a RRH or RRU. Likewise, portions of processing circuitry
1120 may be physically separated from one another. Radio network
equipment 1100 may also include communication interface circuitry
1140 for communicating with other network nodes, e.g., with other
radio network equipment and with nodes in a core network.
Radio front-end circuitry 1110, which may comprise various filters
and amplifiers, for example, is connected to antenna 1105 and
processing circuitry 1120 and is configured to condition signals
communicated between antenna 1105 and processing circuitry 1120. In
certain alternative embodiments, radio network equipment 1100 may
not include radio front-end circuitry 1110, and processing
circuitry 1120 may instead be connected to antenna 1105 without
radio front-end circuitry 1110. In some embodiments,
radio-frequency circuitry 1110 is configured to handle signals in
multiple frequency bands, in some cases simultaneously.
Processing circuitry 1120 may include one or more of RF transceiver
circuitry 1121, baseband processing circuitry 1122, and application
processing circuitry 1123. In some embodiments, the RF transceiver
circuitry 1121, baseband processing circuitry 1122, and application
processing circuitry 1123 may be on separate chipsets. In
alternative embodiments, part or all of the baseband processing
circuitry 1122 and application processing circuitry 1123 may be
combined into one chipset, and the RF transceiver circuitry 1121
may be on a separate chipset. In still alternative embodiments,
part or all of the RF transceiver circuitry 1121 and baseband
processing circuitry 1122 may be on the same chipset, and the
application processing circuitry 1123 may be on a separate chipset.
In yet other alternative embodiments, part or all of the RF
transceiver circuitry 1121, baseband processing circuitry 1122, and
application processing circuitry 1123 may be combined in the same
chipset. Processing circuitry 1120 may include, for example, one or
more central CPUs, one or more microprocessors, one or more ASICs,
and/or one or more field FPGAs.
In particular embodiments, some or all of the functionality
described herein as being relevant to radio network equipment,
radio base stations, eNBs, etc., may be embodied in radio network
equipment or, as an alternative may be embodied by the processing
circuitry 1120 executing instructions stored on a computer-readable
storage medium 1125, as shown in FIG. 18. In alternative
embodiments, some or all of the functionality may be provided by
the processing circuitry 1120 without executing instructions stored
on a computer-readable medium, such as in a hard-wired manner. In
any of those particular embodiments, whether executing instructions
stored on a computer-readable storage medium or not, the processing
circuitry can be said to be configured to perform the described
functionality. The benefits provided by such functionality are not
limited to the processing circuitry 1120 alone or to other
components of the radio network equipment, but are enjoyed by the
radio network equipment 1100 as a whole, and/or by end users and
the wireless network generally.
The processing circuitry 1120 may be configured to perform any
determining operations described herein. Determining as performed
by processing circuitry 1120 may include processing information
obtained by the processing circuitry 1120 by, for example,
converting the obtained information into other information,
comparing the obtained information or converted information to
information stored in the radio network equipment, and/or
performing one or more operations based on the obtained information
or converted information, and as a result of said processing making
a determination.
Antenna 1105, radio front-end circuitry 1110, and/or processing
circuitry 1120 may be configured to perform any transmitting
operations described herein. Any information, data and/or signals
may be transmitted to any network equipment and/or a wireless
device. Likewise, antenna 1105, radio front-end circuitry 1110,
and/or processing circuitry 1120 may be configured to perform any
receiving operations described herein as being performed by a radio
network equipment. Any information, data and/or signals may be
received from any network equipment and/or a wireless device.
Computer-readable storage medium 1125 is generally operable to
store instructions, such as a computer program, software, an
application including one or more of logic, rules, code, tables,
etc. and/or other instructions capable of being executed by a
processor. Examples of computer-readable storage medium 1125
include computer memory (for example, RAM or ROM), mass storage
media (for example, a hard disk), removable storage media (for
example, a CD or a DVD), and/or any other volatile or non-volatile,
non-transitory computer-readable and/or computer-executable memory
devices that store information, data, and/or instructions that may
be used by processing circuitry 1120. In some embodiments,
processing circuitry 1120 and computer-readable storage medium 1125
may be considered to be integrated.
Alternative embodiments of the radio network equipment 1100 may
include additional components beyond those shown in FIG. 18 that
may be responsible for providing certain aspects of the radio
network equipment's functionality, including any of the
functionality described herein and/or any functionality necessary
to support the solution described above. As just one example, radio
network equipment 1100 may include input interfaces, devices and
circuits, and output interfaces, devices and circuits. Input
interfaces, devices, and circuits are configured to allow input of
information into radio network equipment 1100, and are connected to
processing circuitry 1120 to allow processing circuitry 1120 to
process the input information. For example, input interfaces,
devices, and circuits may include a microphone, a proximity or
other sensor, keys/buttons, a touch display, one or more cameras, a
USB port, or other input elements. Output interfaces, devices, and
circuits are configured to allow output of information from radio
network equipment 1100, and are connected to processing circuitry
1120 to allow processing circuitry 1120 to output information from
radio network equipment 1100. For example, output interfaces,
devices, or circuits may include a speaker, a display, a USB port,
a headphone interface, or other output elements. Using one or more
input and output interfaces, devices, and circuits, radio network
equipment 1100 may communicate with end users and/or the wireless
network, and allow them to benefit from the functionality described
herein.
As another example, radio network equipment 1100 may include power
supply circuitry 1130. The power supply circuitry 1130 may comprise
power management circuitry. The power supply circuitry 1130 may
receive power from a power source, which may either be comprised
in, or be external to, power supply circuitry 1130. For example,
radio network equipment 1100 may comprise a power source in the
form of a battery or battery pack which is connected to, or
integrated in, power supply circuitry 1130. Other types of power
sources, such as photovoltaic devices, may also be used. As a
further example, radio network equipment 1100 may be connectable to
an external power source (such as an electricity outlet) via an
input circuitry or interface such as an electrical cable, whereby
the external power source supplies power to power supply circuitry
1130.
Power supply circuitry 1130 may be connected to radio front-end
circuitry 1110, processing circuitry 1120, and/or computer-readable
storage medium 1125 and be configured to supply radio network
equipment 1100, including processing circuitry 1120, with power for
performing the functionality described herein.
Radio network equipment 1100 may also include multiple sets of
processing circuitry 1120, computer-readable storage medium 1125,
radio circuitry 1110, antenna 1105 and/or communication interface
circuitry 1140 for different wireless technologies integrated into
radio network equipment 1100, such as, for example, GSM, WCDMA,
LTE, NR, WiFi, or Bluetooth wireless technologies. These wireless
technologies may be integrated into the same or different chipsets
and other components within radio network equipment 1100.
One or more instances of the radio network equipment 1100 may be
adapted to carry out some or all of the techniques described
herein, in any of various combinations. It will be appreciated that
in a given network implementation, multiple instances of radio
network equipment 1100 will be in use. In some cases, several
instances of radio network equipment 1100 at a time may be
communicating with or transmitting signals to a given wireless
device or group of wireless devices. Thus, it should be understood
that while many of the techniques described herein may be carried
out by a single instance of radio network equipment 1100, these
techniques may be understood as carried out by a system of one or
more instances of radio network equipment 1100, in some cases in a
coordinated fashion. The radio network equipment 1100 shown in FIG.
18 is thus the simplest example of this system.
FIG. 19 illustrates an example functional module or circuit
architecture as may be implemented in a wireless device 1000, e.g.,
based on the processing circuitry 1020. The illustrated embodiment
at least functionally includes a dormant mode module 1910 for
controlling operation of the wireless device 1000 in a dormant
mode, wherein operating in the dormant mode comprises
intermittently activating receiver circuitry to monitor and/or
measure signals. The embodiment further includes several other
modules that operate while the wireless device 1000 is in dormant
mode and while the receiver circuitry is activated, including a
measurement module 1920 for performing a measurement on each of a
plurality of resources from a predetermined set of resources or
demodulating and decoding information from each of a plurality of
resources from a predetermined set of resources, where the
resources in the predetermined set of resources are each defined by
one or more of a beam, a timing, and a frequency, and an evaluation
module 1930 for evaluating the measurement or the demodulated and
decoded information for each of the plurality of resources against
a predetermined criterion.
The illustrated embodiment further includes a discontinuing module
1940 for discontinuing the performing and evaluating of
measurements or discontinuing the demodulating and decoding and
evaluation of information, in response to determining that the
predetermined criterion is met, such that one or more resources in
the predetermined set of resources are neither measured nor
demodulated and decoded, and a deactivation module 1950 for
deactivating the activated receiver circuitry, further in response
to determining that the predetermined criterion is met.
In some embodiments of the wireless device 1000 as illustrated in
FIG. 19, the resources in the predetermined set of resources are
each defined as a beam. In some embodiments, the predetermined
criterion comprises one or more of the following: that a received
power level, or a measured signal-to-interference-plus-noise ratio
(SINR), or a signal-to-noise ratio (SNR) is above a predetermined
threshold, for one or for a predetermined number of resources; that
cell information can be correctly decoded from one or for a
predetermined number of resources; that decoded information from
one or for a predetermined number of resources instructs a change
in operation for the wireless device.
In some embodiments, discontinuing module 1940 is adapted to
perform its discontinuing in response to determining that the
predetermined criterion is met for one of the resources.
In some embodiments, the wireless device 1000 further comprises a
determining module (not pictured) for determining, prior to the
operations carried out by the measurement module 1920, evaluating
module 1930, discontinuing module 1940, and deactivation module
1950, a priority order for the predetermined set of resources, from
highest to lowest. In these embodiments, the operations carried out
by the measurement module are carried out according to the priority
order, from highest to lowest. In some of these embodiments, the
determining of the priority order for the predetermined set of
resources is based on one or more of: radio resource timing for one
or more of the resources; and measured signal qualities or
measurement properties from previous measurements of one or more of
the resources. In some of these and in some other embodiments, the
determining of the priority order for the predetermined set of
resources is based on information regarding likelihood of
usefulness for one or more of the resources, this information being
received from other sources or cell neighbour lists.
* * * * *
References